Presentation outlinePresentation outline
11 Critical functions of immune systemCritical functions of immune system
22 Dual nature Dual nature
33 CharacteristicsCharacteristics
44 FunctionsFunctions
55 Features Features
66 Mechanisms of immune response Mechanisms of immune response
77 Types of immune systems Types of immune systems
The immune system is The immune system is crucial to human crucial to human
survivalsurvivalbull The immune system consists of a The immune system consists of a
complex network of organs cells and complex network of organs cells and moleculesmolecules which work together to defend which work together to defend the body from disease causing organisms the body from disease causing organisms (bacteria viruses fungi and parasites)(bacteria viruses fungi and parasites)
bull The purpose of the immune system is The purpose of the immune system is to to maintain homeostasismaintain homeostasis which includes which includes protecting the body from pathogens and protecting the body from pathogens and toxins that could disrupt the toxins that could disrupt the homeostasishomeostasis
The Bodyrsquos DefensesThe Bodyrsquos DefensesThe Immune SystemThe Immune System
Vertebrate Immune MechanismsVertebrate Immune Mechanismsbull Innate ImmunityInnate Immunitybull Acquired ImmunityAcquired Immunitybull Cell-Mediated ResponseCell-Mediated Responsebull Humoral ResponseHumoral Responsebull Lymphatic TissuesLymphatic Tissues
Multilayered and dual nature of Multilayered and dual nature of the Immune Systemthe Immune System
The architecture of the immune system is multi-layered The architecture of the immune system is multi-layered with defenses on several levels with defenses on several levels Several barriers (external to internal simple to Several barriers (external to internal simple to complex) provided at many levels of infection complex) provided at many levels of infection The immune system has a series of dual naturesThe immune system has a series of dual natures
Self non-self recognitionSelf non-self recognitionNatural adaptiveNatural adaptiveCell mediated humoral Cell mediated humoral Passive activePassive activePrimary secondaryPrimary secondary
bull Both systems consist of a multitude of cells and Both systems consist of a multitude of cells and molecules that interact in a complex manner to detect molecules that interact in a complex manner to detect and eliminate pathogensand eliminate pathogens
Characteristics of the immune Characteristics of the immune responseresponse
11 SpecificitySpecificity the ability to distinguish the ability to distinguish between antigens between antigens
22 AdaptivenessAdaptiveness the ability to respond to the ability to respond to previously unseen moleculespreviously unseen molecules
33 Recognition of self and non-self Recognition of self and non-self the ability the ability to recognize and respond to molecules that to recognize and respond to molecules that are foreign or lsquonon-self lsquoand the molecules are foreign or lsquonon-self lsquoand the molecules that are lsquoselfrsquothat are lsquoselfrsquo
44 MemoryMemory the ability to recall previous the ability to recall previous contact with a foreign molecule and respond contact with a foreign molecule and respond to it in a learned mannerto it in a learned manner
Functions of immune Functions of immune systemsystem
bull The immune system like any organization The immune system like any organization has members that perform different has members that perform different functions to accomplish a common goalfunctions to accomplish a common goal
11 Provides defenses against pathogensProvides defenses against pathogens
22 Removes dead or worn out cells like RBCsRemoves dead or worn out cells like RBCs
33 Identifies and destroys abnormal cancer Identifies and destroys abnormal cancer cellscells
44 Protects from autoimmune diseasesProtects from autoimmune diseases
55 Rejects tissues cells of foreign antigens Rejects tissues cells of foreign antigens
Main features of Immune Main features of Immune system system
Pattern recognitionPattern recognition
(anomaly detection noise (anomaly detection noise tolerance) tolerance)
distributed No central point of distributed No central point of controlcontrol
diversity diversity
learning learning
memory memory
redundancy redundancy
robustness robustness
feature extraction feature extraction
multilayered andmultilayered and
adaptiveadaptive
Mechanism of immune Mechanism of immune responseresponse
bull The immune system specifically recognizes and The immune system specifically recognizes and selectively eliminates pathogensselectively eliminates pathogens
bull There are two critical steps in the immune There are two critical steps in the immune responseresponse11 Detection eventsDetection events22 Elimination eventsElimination events
bull The detection and elimination of pathogens The detection and elimination of pathogens depend upon the chemical bonding between depend upon the chemical bonding between receptors on the surface of an immune cell and receptors on the surface of an immune cell and epitopes found on the surface of a pathogenepitopes found on the surface of a pathogen
bull The The complementary receptor ndash epitope bindingcomplementary receptor ndash epitope binding ( monospecificity) activates a complex system ( monospecificity) activates a complex system of signalling that mediates the immune responseof signalling that mediates the immune response
Mechanism of immune Mechanism of immune responseresponse
bull Immune Immune recognition phaserecognition phase is critical in is critical in the normal functioning of the systemthe normal functioning of the system
bull This is accomplished by three sets of This is accomplished by three sets of antigen binding molecules antigen binding molecules
11 T- cell antigen receptors (TCR)T- cell antigen receptors (TCR)22 Class I and class II molecules of the Class I and class II molecules of the
MHCMHC33 B-cell antigen receptor (BCR B-cell antigen receptor (BCR
immunoglobulin)immunoglobulin)bull The The effector phaseeffector phase is mediated by a is mediated by a
variety of cells and soluble factorsvariety of cells and soluble factors
Immune SystemImmune System
Two types of immune Two types of immune systemsystem
1048698 1048698 Innate Innate immune systemimmune system
1048698 1048698 Adaptive Adaptive immune systemimmune system
Main Types of Immunity in Main Types of Immunity in ManMan
Immunity
Innate immunity
Adaptive immunity
Natural Artificial
Passive (maternal)
Active (Infection)
Passive (Serotherapy)
Active (Vaccination)
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
The immune system is The immune system is crucial to human crucial to human
survivalsurvivalbull The immune system consists of a The immune system consists of a
complex network of organs cells and complex network of organs cells and moleculesmolecules which work together to defend which work together to defend the body from disease causing organisms the body from disease causing organisms (bacteria viruses fungi and parasites)(bacteria viruses fungi and parasites)
bull The purpose of the immune system is The purpose of the immune system is to to maintain homeostasismaintain homeostasis which includes which includes protecting the body from pathogens and protecting the body from pathogens and toxins that could disrupt the toxins that could disrupt the homeostasishomeostasis
The Bodyrsquos DefensesThe Bodyrsquos DefensesThe Immune SystemThe Immune System
Vertebrate Immune MechanismsVertebrate Immune Mechanismsbull Innate ImmunityInnate Immunitybull Acquired ImmunityAcquired Immunitybull Cell-Mediated ResponseCell-Mediated Responsebull Humoral ResponseHumoral Responsebull Lymphatic TissuesLymphatic Tissues
Multilayered and dual nature of Multilayered and dual nature of the Immune Systemthe Immune System
The architecture of the immune system is multi-layered The architecture of the immune system is multi-layered with defenses on several levels with defenses on several levels Several barriers (external to internal simple to Several barriers (external to internal simple to complex) provided at many levels of infection complex) provided at many levels of infection The immune system has a series of dual naturesThe immune system has a series of dual natures
Self non-self recognitionSelf non-self recognitionNatural adaptiveNatural adaptiveCell mediated humoral Cell mediated humoral Passive activePassive activePrimary secondaryPrimary secondary
bull Both systems consist of a multitude of cells and Both systems consist of a multitude of cells and molecules that interact in a complex manner to detect molecules that interact in a complex manner to detect and eliminate pathogensand eliminate pathogens
Characteristics of the immune Characteristics of the immune responseresponse
11 SpecificitySpecificity the ability to distinguish the ability to distinguish between antigens between antigens
22 AdaptivenessAdaptiveness the ability to respond to the ability to respond to previously unseen moleculespreviously unseen molecules
33 Recognition of self and non-self Recognition of self and non-self the ability the ability to recognize and respond to molecules that to recognize and respond to molecules that are foreign or lsquonon-self lsquoand the molecules are foreign or lsquonon-self lsquoand the molecules that are lsquoselfrsquothat are lsquoselfrsquo
44 MemoryMemory the ability to recall previous the ability to recall previous contact with a foreign molecule and respond contact with a foreign molecule and respond to it in a learned mannerto it in a learned manner
Functions of immune Functions of immune systemsystem
bull The immune system like any organization The immune system like any organization has members that perform different has members that perform different functions to accomplish a common goalfunctions to accomplish a common goal
11 Provides defenses against pathogensProvides defenses against pathogens
22 Removes dead or worn out cells like RBCsRemoves dead or worn out cells like RBCs
33 Identifies and destroys abnormal cancer Identifies and destroys abnormal cancer cellscells
44 Protects from autoimmune diseasesProtects from autoimmune diseases
55 Rejects tissues cells of foreign antigens Rejects tissues cells of foreign antigens
Main features of Immune Main features of Immune system system
Pattern recognitionPattern recognition
(anomaly detection noise (anomaly detection noise tolerance) tolerance)
distributed No central point of distributed No central point of controlcontrol
diversity diversity
learning learning
memory memory
redundancy redundancy
robustness robustness
feature extraction feature extraction
multilayered andmultilayered and
adaptiveadaptive
Mechanism of immune Mechanism of immune responseresponse
bull The immune system specifically recognizes and The immune system specifically recognizes and selectively eliminates pathogensselectively eliminates pathogens
bull There are two critical steps in the immune There are two critical steps in the immune responseresponse11 Detection eventsDetection events22 Elimination eventsElimination events
bull The detection and elimination of pathogens The detection and elimination of pathogens depend upon the chemical bonding between depend upon the chemical bonding between receptors on the surface of an immune cell and receptors on the surface of an immune cell and epitopes found on the surface of a pathogenepitopes found on the surface of a pathogen
bull The The complementary receptor ndash epitope bindingcomplementary receptor ndash epitope binding ( monospecificity) activates a complex system ( monospecificity) activates a complex system of signalling that mediates the immune responseof signalling that mediates the immune response
Mechanism of immune Mechanism of immune responseresponse
bull Immune Immune recognition phaserecognition phase is critical in is critical in the normal functioning of the systemthe normal functioning of the system
bull This is accomplished by three sets of This is accomplished by three sets of antigen binding molecules antigen binding molecules
11 T- cell antigen receptors (TCR)T- cell antigen receptors (TCR)22 Class I and class II molecules of the Class I and class II molecules of the
MHCMHC33 B-cell antigen receptor (BCR B-cell antigen receptor (BCR
immunoglobulin)immunoglobulin)bull The The effector phaseeffector phase is mediated by a is mediated by a
variety of cells and soluble factorsvariety of cells and soluble factors
Immune SystemImmune System
Two types of immune Two types of immune systemsystem
1048698 1048698 Innate Innate immune systemimmune system
1048698 1048698 Adaptive Adaptive immune systemimmune system
Main Types of Immunity in Main Types of Immunity in ManMan
Immunity
Innate immunity
Adaptive immunity
Natural Artificial
Passive (maternal)
Active (Infection)
Passive (Serotherapy)
Active (Vaccination)
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
The Bodyrsquos DefensesThe Bodyrsquos DefensesThe Immune SystemThe Immune System
Vertebrate Immune MechanismsVertebrate Immune Mechanismsbull Innate ImmunityInnate Immunitybull Acquired ImmunityAcquired Immunitybull Cell-Mediated ResponseCell-Mediated Responsebull Humoral ResponseHumoral Responsebull Lymphatic TissuesLymphatic Tissues
Multilayered and dual nature of Multilayered and dual nature of the Immune Systemthe Immune System
The architecture of the immune system is multi-layered The architecture of the immune system is multi-layered with defenses on several levels with defenses on several levels Several barriers (external to internal simple to Several barriers (external to internal simple to complex) provided at many levels of infection complex) provided at many levels of infection The immune system has a series of dual naturesThe immune system has a series of dual natures
Self non-self recognitionSelf non-self recognitionNatural adaptiveNatural adaptiveCell mediated humoral Cell mediated humoral Passive activePassive activePrimary secondaryPrimary secondary
bull Both systems consist of a multitude of cells and Both systems consist of a multitude of cells and molecules that interact in a complex manner to detect molecules that interact in a complex manner to detect and eliminate pathogensand eliminate pathogens
Characteristics of the immune Characteristics of the immune responseresponse
11 SpecificitySpecificity the ability to distinguish the ability to distinguish between antigens between antigens
22 AdaptivenessAdaptiveness the ability to respond to the ability to respond to previously unseen moleculespreviously unseen molecules
33 Recognition of self and non-self Recognition of self and non-self the ability the ability to recognize and respond to molecules that to recognize and respond to molecules that are foreign or lsquonon-self lsquoand the molecules are foreign or lsquonon-self lsquoand the molecules that are lsquoselfrsquothat are lsquoselfrsquo
44 MemoryMemory the ability to recall previous the ability to recall previous contact with a foreign molecule and respond contact with a foreign molecule and respond to it in a learned mannerto it in a learned manner
Functions of immune Functions of immune systemsystem
bull The immune system like any organization The immune system like any organization has members that perform different has members that perform different functions to accomplish a common goalfunctions to accomplish a common goal
11 Provides defenses against pathogensProvides defenses against pathogens
22 Removes dead or worn out cells like RBCsRemoves dead or worn out cells like RBCs
33 Identifies and destroys abnormal cancer Identifies and destroys abnormal cancer cellscells
44 Protects from autoimmune diseasesProtects from autoimmune diseases
55 Rejects tissues cells of foreign antigens Rejects tissues cells of foreign antigens
Main features of Immune Main features of Immune system system
Pattern recognitionPattern recognition
(anomaly detection noise (anomaly detection noise tolerance) tolerance)
distributed No central point of distributed No central point of controlcontrol
diversity diversity
learning learning
memory memory
redundancy redundancy
robustness robustness
feature extraction feature extraction
multilayered andmultilayered and
adaptiveadaptive
Mechanism of immune Mechanism of immune responseresponse
bull The immune system specifically recognizes and The immune system specifically recognizes and selectively eliminates pathogensselectively eliminates pathogens
bull There are two critical steps in the immune There are two critical steps in the immune responseresponse11 Detection eventsDetection events22 Elimination eventsElimination events
bull The detection and elimination of pathogens The detection and elimination of pathogens depend upon the chemical bonding between depend upon the chemical bonding between receptors on the surface of an immune cell and receptors on the surface of an immune cell and epitopes found on the surface of a pathogenepitopes found on the surface of a pathogen
bull The The complementary receptor ndash epitope bindingcomplementary receptor ndash epitope binding ( monospecificity) activates a complex system ( monospecificity) activates a complex system of signalling that mediates the immune responseof signalling that mediates the immune response
Mechanism of immune Mechanism of immune responseresponse
bull Immune Immune recognition phaserecognition phase is critical in is critical in the normal functioning of the systemthe normal functioning of the system
bull This is accomplished by three sets of This is accomplished by three sets of antigen binding molecules antigen binding molecules
11 T- cell antigen receptors (TCR)T- cell antigen receptors (TCR)22 Class I and class II molecules of the Class I and class II molecules of the
MHCMHC33 B-cell antigen receptor (BCR B-cell antigen receptor (BCR
immunoglobulin)immunoglobulin)bull The The effector phaseeffector phase is mediated by a is mediated by a
variety of cells and soluble factorsvariety of cells and soluble factors
Immune SystemImmune System
Two types of immune Two types of immune systemsystem
1048698 1048698 Innate Innate immune systemimmune system
1048698 1048698 Adaptive Adaptive immune systemimmune system
Main Types of Immunity in Main Types of Immunity in ManMan
Immunity
Innate immunity
Adaptive immunity
Natural Artificial
Passive (maternal)
Active (Infection)
Passive (Serotherapy)
Active (Vaccination)
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Multilayered and dual nature of Multilayered and dual nature of the Immune Systemthe Immune System
The architecture of the immune system is multi-layered The architecture of the immune system is multi-layered with defenses on several levels with defenses on several levels Several barriers (external to internal simple to Several barriers (external to internal simple to complex) provided at many levels of infection complex) provided at many levels of infection The immune system has a series of dual naturesThe immune system has a series of dual natures
Self non-self recognitionSelf non-self recognitionNatural adaptiveNatural adaptiveCell mediated humoral Cell mediated humoral Passive activePassive activePrimary secondaryPrimary secondary
bull Both systems consist of a multitude of cells and Both systems consist of a multitude of cells and molecules that interact in a complex manner to detect molecules that interact in a complex manner to detect and eliminate pathogensand eliminate pathogens
Characteristics of the immune Characteristics of the immune responseresponse
11 SpecificitySpecificity the ability to distinguish the ability to distinguish between antigens between antigens
22 AdaptivenessAdaptiveness the ability to respond to the ability to respond to previously unseen moleculespreviously unseen molecules
33 Recognition of self and non-self Recognition of self and non-self the ability the ability to recognize and respond to molecules that to recognize and respond to molecules that are foreign or lsquonon-self lsquoand the molecules are foreign or lsquonon-self lsquoand the molecules that are lsquoselfrsquothat are lsquoselfrsquo
44 MemoryMemory the ability to recall previous the ability to recall previous contact with a foreign molecule and respond contact with a foreign molecule and respond to it in a learned mannerto it in a learned manner
Functions of immune Functions of immune systemsystem
bull The immune system like any organization The immune system like any organization has members that perform different has members that perform different functions to accomplish a common goalfunctions to accomplish a common goal
11 Provides defenses against pathogensProvides defenses against pathogens
22 Removes dead or worn out cells like RBCsRemoves dead or worn out cells like RBCs
33 Identifies and destroys abnormal cancer Identifies and destroys abnormal cancer cellscells
44 Protects from autoimmune diseasesProtects from autoimmune diseases
55 Rejects tissues cells of foreign antigens Rejects tissues cells of foreign antigens
Main features of Immune Main features of Immune system system
Pattern recognitionPattern recognition
(anomaly detection noise (anomaly detection noise tolerance) tolerance)
distributed No central point of distributed No central point of controlcontrol
diversity diversity
learning learning
memory memory
redundancy redundancy
robustness robustness
feature extraction feature extraction
multilayered andmultilayered and
adaptiveadaptive
Mechanism of immune Mechanism of immune responseresponse
bull The immune system specifically recognizes and The immune system specifically recognizes and selectively eliminates pathogensselectively eliminates pathogens
bull There are two critical steps in the immune There are two critical steps in the immune responseresponse11 Detection eventsDetection events22 Elimination eventsElimination events
bull The detection and elimination of pathogens The detection and elimination of pathogens depend upon the chemical bonding between depend upon the chemical bonding between receptors on the surface of an immune cell and receptors on the surface of an immune cell and epitopes found on the surface of a pathogenepitopes found on the surface of a pathogen
bull The The complementary receptor ndash epitope bindingcomplementary receptor ndash epitope binding ( monospecificity) activates a complex system ( monospecificity) activates a complex system of signalling that mediates the immune responseof signalling that mediates the immune response
Mechanism of immune Mechanism of immune responseresponse
bull Immune Immune recognition phaserecognition phase is critical in is critical in the normal functioning of the systemthe normal functioning of the system
bull This is accomplished by three sets of This is accomplished by three sets of antigen binding molecules antigen binding molecules
11 T- cell antigen receptors (TCR)T- cell antigen receptors (TCR)22 Class I and class II molecules of the Class I and class II molecules of the
MHCMHC33 B-cell antigen receptor (BCR B-cell antigen receptor (BCR
immunoglobulin)immunoglobulin)bull The The effector phaseeffector phase is mediated by a is mediated by a
variety of cells and soluble factorsvariety of cells and soluble factors
Immune SystemImmune System
Two types of immune Two types of immune systemsystem
1048698 1048698 Innate Innate immune systemimmune system
1048698 1048698 Adaptive Adaptive immune systemimmune system
Main Types of Immunity in Main Types of Immunity in ManMan
Immunity
Innate immunity
Adaptive immunity
Natural Artificial
Passive (maternal)
Active (Infection)
Passive (Serotherapy)
Active (Vaccination)
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Characteristics of the immune Characteristics of the immune responseresponse
11 SpecificitySpecificity the ability to distinguish the ability to distinguish between antigens between antigens
22 AdaptivenessAdaptiveness the ability to respond to the ability to respond to previously unseen moleculespreviously unseen molecules
33 Recognition of self and non-self Recognition of self and non-self the ability the ability to recognize and respond to molecules that to recognize and respond to molecules that are foreign or lsquonon-self lsquoand the molecules are foreign or lsquonon-self lsquoand the molecules that are lsquoselfrsquothat are lsquoselfrsquo
44 MemoryMemory the ability to recall previous the ability to recall previous contact with a foreign molecule and respond contact with a foreign molecule and respond to it in a learned mannerto it in a learned manner
Functions of immune Functions of immune systemsystem
bull The immune system like any organization The immune system like any organization has members that perform different has members that perform different functions to accomplish a common goalfunctions to accomplish a common goal
11 Provides defenses against pathogensProvides defenses against pathogens
22 Removes dead or worn out cells like RBCsRemoves dead or worn out cells like RBCs
33 Identifies and destroys abnormal cancer Identifies and destroys abnormal cancer cellscells
44 Protects from autoimmune diseasesProtects from autoimmune diseases
55 Rejects tissues cells of foreign antigens Rejects tissues cells of foreign antigens
Main features of Immune Main features of Immune system system
Pattern recognitionPattern recognition
(anomaly detection noise (anomaly detection noise tolerance) tolerance)
distributed No central point of distributed No central point of controlcontrol
diversity diversity
learning learning
memory memory
redundancy redundancy
robustness robustness
feature extraction feature extraction
multilayered andmultilayered and
adaptiveadaptive
Mechanism of immune Mechanism of immune responseresponse
bull The immune system specifically recognizes and The immune system specifically recognizes and selectively eliminates pathogensselectively eliminates pathogens
bull There are two critical steps in the immune There are two critical steps in the immune responseresponse11 Detection eventsDetection events22 Elimination eventsElimination events
bull The detection and elimination of pathogens The detection and elimination of pathogens depend upon the chemical bonding between depend upon the chemical bonding between receptors on the surface of an immune cell and receptors on the surface of an immune cell and epitopes found on the surface of a pathogenepitopes found on the surface of a pathogen
bull The The complementary receptor ndash epitope bindingcomplementary receptor ndash epitope binding ( monospecificity) activates a complex system ( monospecificity) activates a complex system of signalling that mediates the immune responseof signalling that mediates the immune response
Mechanism of immune Mechanism of immune responseresponse
bull Immune Immune recognition phaserecognition phase is critical in is critical in the normal functioning of the systemthe normal functioning of the system
bull This is accomplished by three sets of This is accomplished by three sets of antigen binding molecules antigen binding molecules
11 T- cell antigen receptors (TCR)T- cell antigen receptors (TCR)22 Class I and class II molecules of the Class I and class II molecules of the
MHCMHC33 B-cell antigen receptor (BCR B-cell antigen receptor (BCR
immunoglobulin)immunoglobulin)bull The The effector phaseeffector phase is mediated by a is mediated by a
variety of cells and soluble factorsvariety of cells and soluble factors
Immune SystemImmune System
Two types of immune Two types of immune systemsystem
1048698 1048698 Innate Innate immune systemimmune system
1048698 1048698 Adaptive Adaptive immune systemimmune system
Main Types of Immunity in Main Types of Immunity in ManMan
Immunity
Innate immunity
Adaptive immunity
Natural Artificial
Passive (maternal)
Active (Infection)
Passive (Serotherapy)
Active (Vaccination)
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Functions of immune Functions of immune systemsystem
bull The immune system like any organization The immune system like any organization has members that perform different has members that perform different functions to accomplish a common goalfunctions to accomplish a common goal
11 Provides defenses against pathogensProvides defenses against pathogens
22 Removes dead or worn out cells like RBCsRemoves dead or worn out cells like RBCs
33 Identifies and destroys abnormal cancer Identifies and destroys abnormal cancer cellscells
44 Protects from autoimmune diseasesProtects from autoimmune diseases
55 Rejects tissues cells of foreign antigens Rejects tissues cells of foreign antigens
Main features of Immune Main features of Immune system system
Pattern recognitionPattern recognition
(anomaly detection noise (anomaly detection noise tolerance) tolerance)
distributed No central point of distributed No central point of controlcontrol
diversity diversity
learning learning
memory memory
redundancy redundancy
robustness robustness
feature extraction feature extraction
multilayered andmultilayered and
adaptiveadaptive
Mechanism of immune Mechanism of immune responseresponse
bull The immune system specifically recognizes and The immune system specifically recognizes and selectively eliminates pathogensselectively eliminates pathogens
bull There are two critical steps in the immune There are two critical steps in the immune responseresponse11 Detection eventsDetection events22 Elimination eventsElimination events
bull The detection and elimination of pathogens The detection and elimination of pathogens depend upon the chemical bonding between depend upon the chemical bonding between receptors on the surface of an immune cell and receptors on the surface of an immune cell and epitopes found on the surface of a pathogenepitopes found on the surface of a pathogen
bull The The complementary receptor ndash epitope bindingcomplementary receptor ndash epitope binding ( monospecificity) activates a complex system ( monospecificity) activates a complex system of signalling that mediates the immune responseof signalling that mediates the immune response
Mechanism of immune Mechanism of immune responseresponse
bull Immune Immune recognition phaserecognition phase is critical in is critical in the normal functioning of the systemthe normal functioning of the system
bull This is accomplished by three sets of This is accomplished by three sets of antigen binding molecules antigen binding molecules
11 T- cell antigen receptors (TCR)T- cell antigen receptors (TCR)22 Class I and class II molecules of the Class I and class II molecules of the
MHCMHC33 B-cell antigen receptor (BCR B-cell antigen receptor (BCR
immunoglobulin)immunoglobulin)bull The The effector phaseeffector phase is mediated by a is mediated by a
variety of cells and soluble factorsvariety of cells and soluble factors
Immune SystemImmune System
Two types of immune Two types of immune systemsystem
1048698 1048698 Innate Innate immune systemimmune system
1048698 1048698 Adaptive Adaptive immune systemimmune system
Main Types of Immunity in Main Types of Immunity in ManMan
Immunity
Innate immunity
Adaptive immunity
Natural Artificial
Passive (maternal)
Active (Infection)
Passive (Serotherapy)
Active (Vaccination)
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Main features of Immune Main features of Immune system system
Pattern recognitionPattern recognition
(anomaly detection noise (anomaly detection noise tolerance) tolerance)
distributed No central point of distributed No central point of controlcontrol
diversity diversity
learning learning
memory memory
redundancy redundancy
robustness robustness
feature extraction feature extraction
multilayered andmultilayered and
adaptiveadaptive
Mechanism of immune Mechanism of immune responseresponse
bull The immune system specifically recognizes and The immune system specifically recognizes and selectively eliminates pathogensselectively eliminates pathogens
bull There are two critical steps in the immune There are two critical steps in the immune responseresponse11 Detection eventsDetection events22 Elimination eventsElimination events
bull The detection and elimination of pathogens The detection and elimination of pathogens depend upon the chemical bonding between depend upon the chemical bonding between receptors on the surface of an immune cell and receptors on the surface of an immune cell and epitopes found on the surface of a pathogenepitopes found on the surface of a pathogen
bull The The complementary receptor ndash epitope bindingcomplementary receptor ndash epitope binding ( monospecificity) activates a complex system ( monospecificity) activates a complex system of signalling that mediates the immune responseof signalling that mediates the immune response
Mechanism of immune Mechanism of immune responseresponse
bull Immune Immune recognition phaserecognition phase is critical in is critical in the normal functioning of the systemthe normal functioning of the system
bull This is accomplished by three sets of This is accomplished by three sets of antigen binding molecules antigen binding molecules
11 T- cell antigen receptors (TCR)T- cell antigen receptors (TCR)22 Class I and class II molecules of the Class I and class II molecules of the
MHCMHC33 B-cell antigen receptor (BCR B-cell antigen receptor (BCR
immunoglobulin)immunoglobulin)bull The The effector phaseeffector phase is mediated by a is mediated by a
variety of cells and soluble factorsvariety of cells and soluble factors
Immune SystemImmune System
Two types of immune Two types of immune systemsystem
1048698 1048698 Innate Innate immune systemimmune system
1048698 1048698 Adaptive Adaptive immune systemimmune system
Main Types of Immunity in Main Types of Immunity in ManMan
Immunity
Innate immunity
Adaptive immunity
Natural Artificial
Passive (maternal)
Active (Infection)
Passive (Serotherapy)
Active (Vaccination)
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Mechanism of immune Mechanism of immune responseresponse
bull The immune system specifically recognizes and The immune system specifically recognizes and selectively eliminates pathogensselectively eliminates pathogens
bull There are two critical steps in the immune There are two critical steps in the immune responseresponse11 Detection eventsDetection events22 Elimination eventsElimination events
bull The detection and elimination of pathogens The detection and elimination of pathogens depend upon the chemical bonding between depend upon the chemical bonding between receptors on the surface of an immune cell and receptors on the surface of an immune cell and epitopes found on the surface of a pathogenepitopes found on the surface of a pathogen
bull The The complementary receptor ndash epitope bindingcomplementary receptor ndash epitope binding ( monospecificity) activates a complex system ( monospecificity) activates a complex system of signalling that mediates the immune responseof signalling that mediates the immune response
Mechanism of immune Mechanism of immune responseresponse
bull Immune Immune recognition phaserecognition phase is critical in is critical in the normal functioning of the systemthe normal functioning of the system
bull This is accomplished by three sets of This is accomplished by three sets of antigen binding molecules antigen binding molecules
11 T- cell antigen receptors (TCR)T- cell antigen receptors (TCR)22 Class I and class II molecules of the Class I and class II molecules of the
MHCMHC33 B-cell antigen receptor (BCR B-cell antigen receptor (BCR
immunoglobulin)immunoglobulin)bull The The effector phaseeffector phase is mediated by a is mediated by a
variety of cells and soluble factorsvariety of cells and soluble factors
Immune SystemImmune System
Two types of immune Two types of immune systemsystem
1048698 1048698 Innate Innate immune systemimmune system
1048698 1048698 Adaptive Adaptive immune systemimmune system
Main Types of Immunity in Main Types of Immunity in ManMan
Immunity
Innate immunity
Adaptive immunity
Natural Artificial
Passive (maternal)
Active (Infection)
Passive (Serotherapy)
Active (Vaccination)
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Mechanism of immune Mechanism of immune responseresponse
bull Immune Immune recognition phaserecognition phase is critical in is critical in the normal functioning of the systemthe normal functioning of the system
bull This is accomplished by three sets of This is accomplished by three sets of antigen binding molecules antigen binding molecules
11 T- cell antigen receptors (TCR)T- cell antigen receptors (TCR)22 Class I and class II molecules of the Class I and class II molecules of the
MHCMHC33 B-cell antigen receptor (BCR B-cell antigen receptor (BCR
immunoglobulin)immunoglobulin)bull The The effector phaseeffector phase is mediated by a is mediated by a
variety of cells and soluble factorsvariety of cells and soluble factors
Immune SystemImmune System
Two types of immune Two types of immune systemsystem
1048698 1048698 Innate Innate immune systemimmune system
1048698 1048698 Adaptive Adaptive immune systemimmune system
Main Types of Immunity in Main Types of Immunity in ManMan
Immunity
Innate immunity
Adaptive immunity
Natural Artificial
Passive (maternal)
Active (Infection)
Passive (Serotherapy)
Active (Vaccination)
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Immune SystemImmune System
Two types of immune Two types of immune systemsystem
1048698 1048698 Innate Innate immune systemimmune system
1048698 1048698 Adaptive Adaptive immune systemimmune system
Main Types of Immunity in Main Types of Immunity in ManMan
Immunity
Innate immunity
Adaptive immunity
Natural Artificial
Passive (maternal)
Active (Infection)
Passive (Serotherapy)
Active (Vaccination)
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Main Types of Immunity in Main Types of Immunity in ManMan
Immunity
Innate immunity
Adaptive immunity
Natural Artificial
Passive (maternal)
Active (Infection)
Passive (Serotherapy)
Active (Vaccination)
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Innate ImmunityInnate Immunitybull responds immediatelyresponds immediatelybull protects the body from all foreign substancesprotects the body from all foreign substancesbull functions on two levelsfunctions on two levelsbull first line of defense ndash prevents entry of first line of defense ndash prevents entry of
pathogenspathogensbull mechanical barriersmechanical barriers
skin mucosa and secretionsskin mucosa and secretionsbull second line of defense ndash inhibits spread of second line of defense ndash inhibits spread of
pathogenpathogenbull antimicrobial proteinsantimicrobial proteinsbull phagocytes and other cellsphagocytes and other cellsbull inflammationinflammation
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Three Lines of DefenseThree Lines of Defense
1st Line ndash barriers at portals of entry1st Line ndash barriers at portals of entry10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
2nd Line ndash protective cells and chemicals2nd Line ndash protective cells and chemicals10486981048698come into play when barriers are breachedcome into play when barriers are breached10486981048698primarily inborn and nonspecificprimarily inborn and nonspecific
3rd Line ndash antibodies and cytotoxic cells3rd Line ndash antibodies and cytotoxic cells10486981048698provides long-term immunity after provides long-term immunity after encountersencounters10486981048698primarily acquired and specificprimarily acquired and specific
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Lines of defenseLines of defensebull 11stst lines of defense lines of defense are the physical barriers which include are the physical barriers which include
the skin urine tears ciliary elevator mucosal membrane etcthe skin urine tears ciliary elevator mucosal membrane etc
bull 22ndnd lines of defense lines of defense are the macrophage system are the macrophage system complement fever interferon and inflammation complement fever interferon and inflammation
bull 33rdrd lines of defense lines of defense aare the specific system also known re the specific system also known as acquired or adaptive immunity The specific system consists of B cells (humoral) and T cells (cell-mediated)
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Physical and Chemical Physical and Chemical DefensesDefenses
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
First line of defense-1First line of defense-1
bull The first line of defense are The first line of defense are barrier barrier tissuestissues such as the skin that stop the such as the skin that stop the entry of pathogens into our bodiesentry of pathogens into our bodies
bull If these barrier layers are If these barrier layers are penetrated cells like penetrated cells like macrophages macrophages and neutrophilsand neutrophils engulf foreign engulf foreign organisms and kill them without the organisms and kill them without the need for antibodies need for antibodies
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
First Line of Defense-2First Line of Defense-2
bull SkinSkin provides an almost impenetrable provides an almost impenetrable biological barrier biological barrier
bull Lysozyme Lysozyme is an enzyme found in tears is an enzyme found in tears and saliva that and saliva that can break down foreign can break down foreign agents agents
bull The clotting of blood near open wounds The clotting of blood near open wounds prevents an open space for antigensprevents an open space for antigens
bull Mucus and cilia found in the nose and Mucus and cilia found in the nose and throat can catch foreign agents then throat can catch foreign agents then sweep them outside via sweep them outside via coughing coughing sneezing and vomiting sneezing and vomiting
bull The cell wall of plants consists of The cell wall of plants consists of fibrous fibrous proteinsproteins which provide a barrier to which provide a barrier to potential parasites (antigens) potential parasites (antigens)
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
A second line of defense-1A second line of defense-1
bull A second line of defense is the specific or A second line of defense is the specific or adaptive adaptive immune systemimmune system which may take days to respond which may take days to respond to a primary invasion to a primary invasion
bull The The production of antibodies and cell-mediated production of antibodies and cell-mediated responsesresponses may occur in which specific cells may occur in which specific cells recognize foreign pathogens and destroy themrecognize foreign pathogens and destroy them
bull The response is often more rapid because of the The response is often more rapid because of the activation of memory B and T cellsactivation of memory B and T cells
bull cells of the immune system interact with one cells of the immune system interact with one another by a variety of another by a variety of signal moleculessignal molecules
bull These signals may be proteins such as These signals may be proteins such as lymphokines cytokines and chemokineslymphokines cytokines and chemokines which which stimulate cells of the immune system stimulate cells of the immune system
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Second Line of Defense-2Second Line of Defense-2
bull Second lines of defense deal with Second lines of defense deal with antigens that have bypassed the first antigens that have bypassed the first lines of defense lines of defense
bull InterferonsInterferons are a family of proteins that are a family of proteins that are released by a cell that is under are released by a cell that is under attack by an antigen attack by an antigen
bull One method of attacking antigens is by One method of attacking antigens is by phagocytosisphagocytosis where the contents of where the contents of the antigen are broken down by the antigen are broken down by molecules called phagocytesmolecules called phagocytes
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Adaptive immunityAdaptive immunity
bull The The second levelsecond level of defence increases in of defence increases in strength and effectiveness with each strength and effectiveness with each encounter The foreign agent is recognised encounter The foreign agent is recognised in a specific manner and the immune system in a specific manner and the immune system acquires memory towards it acquires memory towards it
bull The first encounter with an antigen is The first encounter with an antigen is known as known as the primary responsethe primary response Re- Re-encounter with the same antigen causes a encounter with the same antigen causes a secondary responsesecondary response that is more rapid and that is more rapid and powerfulpowerful
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Adaptive immunityAdaptive immunitybull As response produce antibodies to specific As response produce antibodies to specific
infectionsinfections
Some featuresSome features
ndash ndash MemoryMemorybull Each successive encounter with the same Each successive encounter with the same
pathogen improve the responsepathogen improve the response
ndash ndash Clonal selectionClonal selectionbull Select the best and matured immune cells Select the best and matured immune cells
to defend the organism against infectionsto defend the organism against infections
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
bull Whenever T cells and B cells are activated Whenever T cells and B cells are activated some become some become memory cellsmemory cells The next time The next time that an individual encounters that same that an individual encounters that same antigen the immune system is primed to antigen the immune system is primed to destroy it quickly This is destroy it quickly This is active immunityactive immunity
bull Long-term active immunityLong-term active immunity can be naturally can be naturally acquired by infection or artificially acquired acquired by infection or artificially acquired by vaccines by vaccines
bull Short-term passive immunityShort-term passive immunity can be can be transferred artificially from one individual to transferred artificially from one individual to another via antibody-rich serum another via antibody-rich serum
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Active and Passive Acquired Active and Passive Acquired ImmunityImmunity
bull Active immunityActive immunity
ndash Conferred by recovery from infectious diseaseConferred by recovery from infectious disease
ndash Depends on persons own immune systemDepends on persons own immune system
ndash May be acquired artificially with May be acquired artificially with vaccinesvaccines
bull Passive immunityPassive immunity
ndash transferred from person to person through transfer of antibodiestransferred from person to person through transfer of antibodies
ndash Natural instances include antibodies passing across placenta from Natural instances include antibodies passing across placenta from mother to fetus (provides temporary protection) or through the mother to fetus (provides temporary protection) or through the milkmilk
ndash Transferred artificially Eg antibody injections for rabies anti Transferred artificially Eg antibody injections for rabies anti rhesus factor snake venom botulinun toxinrhesus factor snake venom botulinun toxin
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
bull Lymphatic vessels are responsible for flow of lymph Lymphatic vessels are responsible for flow of lymph within the lymphoid system within the lymphoid system
bull Plasma constantly leaks out of capillaries to deliver Plasma constantly leaks out of capillaries to deliver oxygen and nutrients to cells of the surrounding oxygen and nutrients to cells of the surrounding tissue Once in the tissue the plasma is now called tissue Once in the tissue the plasma is now called tissue fluidtissue fluid
bull While most of this tissue fluid re-enters capillaries While most of this tissue fluid re-enters capillaries and is returned directly to the bloodstream some and is returned directly to the bloodstream some fluid enters lymph vessels as fluid enters lymph vessels as lymph lymph
bull LYMPH-LYMPH- flows from the intercellular tissue spaces flows from the intercellular tissue spaces into lymphatic capillaries and then into a series of into lymphatic capillaries and then into a series of larger collecting vessels called larger collecting vessels called lymphatic vesselslymphatic vessels Lymphatic vessels converge into Lymphatic vessels converge into the thoracic ductthe thoracic duct which returns the fluid to the circulatory system by which returns the fluid to the circulatory system by dumping into the left dumping into the left subclavian vein subclavian vein
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Thoracicduct
Overview of blood and lymph system and how Overview of blood and lymph system and how leukocytes travel from one system to anotherleukocytes travel from one system to another
Site of exchange between theblood and lymph systems
Lymph carrying antibodiesand immune cells collect in thoracic duct where the lymph empties back into the blood circulatory system
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Immune cells travel back and forth from Immune cells travel back and forth from the blood and lymph circulatory systems the blood and lymph circulatory systems and interact with extra-vascular tissues and interact with extra-vascular tissues
in the process--in the process--extravasationextravasation
muscle
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Lymphatic vessels Lymphatic vessels
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
The organs of the The organs of the immune system immune system
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Kinds of lymphoid Kinds of lymphoid OrgansOrgans
Primarycentral lymphoid organsPrimarycentral lymphoid organs ndash bone marrow bone marrow ndash thymus thymus
Secondary peripheral lymphoid tissueSecondary peripheral lymphoid tissuendash lymph nodes lymph nodes ndash spleenspleenndash mucosa-associated lymphoid tissuemucosa-associated lymphoid tissue
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Kinds of Lymphoid Organs Kinds of Lymphoid Organs The Lymphoid
Organs
Primary or Central organs
Secondary or Peripheral organs
1Bone marrow2Thymus gland3Bursa of fabricius
1Lymp nodes 2Spleen
3Diffuse lymphoid tissues
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
bull The The bone marrowbone marrow and the and the thymusthymus constitute constitute the primary lymphoid organsthe primary lymphoid organs
bull Both Both B-lymphocytesB-lymphocytes and and T-lymphocytesT-lymphocytes are are produced from stem cells in the bone produced from stem cells in the bone marrow marrow B-lymphocytes mature in the B-lymphocytes mature in the bone marrow while T-lymphocytes bone marrow while T-lymphocytes migrate to the thymus and mature migrate to the thymus and mature therethere
bull After maturation both B-lymphocytes and T-After maturation both B-lymphocytes and T-lymphocytes circulate through and lymphocytes circulate through and accumulate in accumulate in secondary lymphoid organssecondary lymphoid organs
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
bull The secondary lymphoid organs include lymph nodes The secondary lymphoid organs include lymph nodes and the spleen as well as lymphoid tissues and the spleen as well as lymphoid tissues
bull The lymphoid tissues include The lymphoid tissues include the tonsils the the tonsils the appendix the Peyers patchesappendix the Peyers patches in the lining of the in the lining of the small intestines (small intestines (gut-associated lymphoid tissue or gut-associated lymphoid tissue or GALTGALT) )
bull The lymphoid tissue found beneath the mucous The lymphoid tissue found beneath the mucous membranes of the bronchi (membranes of the bronchi (bronchial-associated bronchial-associated lymphoid tissue or BALTlymphoid tissue or BALT) )
bull The lymphatic tissue found in the mucous The lymphatic tissue found in the mucous membranes (membranes (mucosa-associated lymphoid tissue or mucosa-associated lymphoid tissue or MALTMALT))
bull The lymphatic tissue found beneath the skin (The lymphatic tissue found beneath the skin (skin-skin-associated lymphoid tissue or SALTassociated lymphoid tissue or SALT) )
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Primary and SecondaryPrimary and Secondary Lymphoid organs Lymphoid organs
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Primarycentral lymphoid Primarycentral lymphoid organs organs
BONE MARROWBONE MARROW is a central organ is a central organ where all the immune cells are where all the immune cells are born and only B cells mature born and only B cells mature (process termed as (process termed as B B lymphopoiesis) lymphopoiesis)
THYMUSTHYMUS is the other central organ is the other central organ in which T cells mature (in which T cells mature (T T lymphopoiesislymphopoiesis) )
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
The bone marrowThe bone marrow
Bone marrow is a spongy tissue found Bone marrow is a spongy tissue found within boneswithin bonesAll blood cells are produced within the bone All blood cells are produced within the bone marrowmarrowThe bone marrow of an adult produce about The bone marrow of an adult produce about three million red blood cells and 120000 three million red blood cells and 120000 white blood cells every second white blood cells every second All these cells originate from a small All these cells originate from a small population of stem cells which may be as population of stem cells which may be as few as one in a million of the bone marrow few as one in a million of the bone marrow cells cells
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
ThymuThymuss
bullThe thymus is an organ located in the The thymus is an organ located in the upper chestupper chest bullImmature lymphocytes leave the bone Immature lymphocytes leave the bone marrow and find their way to the thymus marrow and find their way to the thymus where they are ldquoeducatedrdquo to become where they are ldquoeducatedrdquo to become mature T-lymphocytesmature T-lymphocytes
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
ThymusThymusFlat bilobed organ situated above the heart Flat bilobed organ situated above the heart
and below the thyroid glandand below the thyroid gland Each lobe is surrounded by a capsule and is Each lobe is surrounded by a capsule and is
divided into lobules divided into lobules The lobules are separated from each other by The lobules are separated from each other by
strands of connective tissue called strands of connective tissue called trabeculaetrabeculae
Each lobule is organized into two Each lobule is organized into two compartments the compartments the cortex cortex (outer (outer compartment) the compartment) the medullamedulla (inner (inner compartment) compartment)
bull Cortex and Medulla are both crisscrossed by Cortex and Medulla are both crisscrossed by a a network of stromal cellsnetwork of stromal cells composed of composed of
bull loosely packed thymic epithelial cells loosely packed thymic epithelial cells bull interdigitating dendritic cells interdigitating dendritic cells bull macrophages macrophages
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
ThymusThymusbull In the cortex the network is densely packed with In the cortex the network is densely packed with
thymocytes thymocytes Cells are less dense in medullaCells are less dense in medulla bull In medulla the epithelial cells are more visible In medulla the epithelial cells are more visible
and and HASSALs Corpuscles are presentHASSALs Corpuscles are present (Function (Function Unknown) Unknown)
bull The thymus is at its lThe thymus is at its largest relative size at birthargest relative size at birth and its land its largest actual size is at pubertyargest actual size is at puberty
bull After puberty the thymus begins to shrink In After puberty the thymus begins to shrink In elderly individuals it is usually less than 3 grams elderly individuals it is usually less than 3 grams in weight in weight
bull There is relationship between aging and a decline There is relationship between aging and a decline in immune responsiveness in immune responsiveness
bull Stress can also result in shrinkage of the thymus Stress can also result in shrinkage of the thymus
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
ThymusThymusbull Precursor T cells enter thymus from the Precursor T cells enter thymus from the
blood (blood (there are no afferent lymphatic there are no afferent lymphatic vesselsvessels] and mature into functional T ] and mature into functional T lymphocyteslymphocytes
bull However the vast majority of these cells However the vast majority of these cells are destined to die due to (APOPTOSIS) - are destined to die due to (APOPTOSIS) - programmed cell deathprogrammed cell death
bull The T cells (thymocytes) go through a The T cells (thymocytes) go through a selection process in the thymus based selection process in the thymus based upon the TcR that they possess upon the TcR that they possess
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Process of thymic educationProcess of thymic educationbull The complete process of thymic education is a The complete process of thymic education is a
two-step process in which Thymic cortical two-step process in which Thymic cortical epithelial cells function as the effector cells in a epithelial cells function as the effector cells in a process known as process known as POSITIVE SELECTIONPOSITIVE SELECTION
bull In positive selection T cells which bear a TcR In positive selection T cells which bear a TcR which which can bindcan bind SELF-MHC are selected to survive SELF-MHC are selected to survive and proliferate Cells which are not positively and proliferate Cells which are not positively selected are triggered to undergo APOPTOSIS selected are triggered to undergo APOPTOSIS
bull Positively selected thymocytes must go through a Positively selected thymocytes must go through a second phase of selection known as second phase of selection known as NEGATIVE NEGATIVE SELECTIONSELECTION
bull Functionally during negative selection any T cell Functionally during negative selection any T cell that is presented antigen + MHC within the that is presented antigen + MHC within the thymus is triggered to undergo APOPTOSIS thymus is triggered to undergo APOPTOSIS
bull Most importantly thymic macrophages and Most importantly thymic macrophages and dendritic cells serve as APCs in the process of dendritic cells serve as APCs in the process of negative selection negative selection
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Thymic hormones Thymic hormones
bull Stromal cells secrete soluble factors Stromal cells secrete soluble factors which are important in T cell maturation which are important in T cell maturation
bull Some examples includeSome examples include alpha- 1- thymosin alpha- 1- thymosin beta - 4- thymosin beta - 4- thymosin thymopoietin thymopoietin thymulin thymulin
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Lymph nodesLymph nodesbull Small bean-shaped Small bean-shaped lymph nodes lymph nodes are laced are laced
along the lymphatic vessels with clusters along the lymphatic vessels with clusters in the neck armpits abdomen and groinin the neck armpits abdomen and groin
bull Each lymph node contains specialized Each lymph node contains specialized compartments where immune cells compartments where immune cells congregate and where they can encounter congregate and where they can encounter antigensantigens
bull Immune cells and foreign particles enter Immune cells and foreign particles enter the lymph nodes via incoming lymphatic the lymph nodes via incoming lymphatic vessels All lymphocytes exit lymph nodes vessels All lymphocytes exit lymph nodes through outgoing lymphatic vesselsthrough outgoing lymphatic vessels
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Lymph NodeLymph Node
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
The regions of Lymph The regions of Lymph nodenode
3 regions to the lymph node 3 regions to the lymph node bull CortexCortex (outermost layer- (outermost layer- contains mostly B contains mostly B
lymphocyteslymphocytes plus both follicular dendritic cells and plus both follicular dendritic cells and macrophages all arranged in clusters called macrophages all arranged in clusters called primary primary folliclesfollicles))
bull Following antigenic stimulation the primary Following antigenic stimulation the primary follicles become follicles become secondary folliclessecondary follicles consisting of consisting of concentric rings of densely packed lymphocytes concentric rings of densely packed lymphocytes and central lymphocytes macrophages and and central lymphocytes macrophages and dendritic cells dendritic cells
bull The The GCs (germinal centers)GCs (germinal centers) contain large contain large proliferating B lymphocytes and plasma cells proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells interspersed with macrophages and dendritic cells
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
The regions of Lymph The regions of Lymph nodenode
bull The GC is a site of intense B-Cell activation and The GC is a site of intense B-Cell activation and differentiation into plasma cells and memory differentiation into plasma cells and memory cellscells
bull ParacortexParacortex - (layer just beneath the cortex) This - (layer just beneath the cortex) This region is sometimes called the T dependent region is sometimes called the T dependent region of the lymph node region of the lymph node It is an area populated with T lymphocytes and It is an area populated with T lymphocytes and also interdigitating dendritic cells It is an also interdigitating dendritic cells It is an important site for T cell activation by these APCs important site for T cell activation by these APCs
bull MedullaMedulla- inner most region more sparsely - inner most region more sparsely populated by cells Many of the cells are plasma populated by cells Many of the cells are plasma cells activated Th and Tc are also present In cells activated Th and Tc are also present In addition there is a high concentration of addition there is a high concentration of immunoglobulin in this region due to the large immunoglobulin in this region due to the large population of plasma cells population of plasma cells
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Swelling of lymph nodes Swelling of lymph nodes
bull This huge increase in the number of This huge increase in the number of lymphocytes is due tolymphocytes is due to
bull proliferation of lymphocytes within the lymph proliferation of lymphocytes within the lymph node node
bull influx of lymphocytes from the circulatory influx of lymphocytes from the circulatory system system
bull -Clearly the concentration of lymphocytes in -Clearly the concentration of lymphocytes in the lymph nodes can increase greatly the lymph nodes can increase greatly following antigenic stimulation accounting for following antigenic stimulation accounting for swelling of lymph nodesswelling of lymph nodes
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
The spleenThe spleenbull The spleen is the largest of the The spleen is the largest of the
lymphoid organs lymphoid organs bull The The spleen spleen is a flattened organ at the is a flattened organ at the
upper left of the abdomen upper left of the abdomen bull Like the lymph nodes the spleen Like the lymph nodes the spleen
contains specialized compartments contains specialized compartments where immune cells gather and work where immune cells gather and work and serves as a meeting ground where and serves as a meeting ground where immune defenses confront antigensimmune defenses confront antigens
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
SpleenSpleen
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
SpleenSpleen
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Spleen Spleen
bull The spleen is adapted The spleen is adapted to filter theto filter the bloodblood it responds therefore to it responds therefore to systemic systemic infectionsinfections
bull It is surrounded by a capsule which It is surrounded by a capsule which sends trabeculae into the interior to sends trabeculae into the interior to form a compartmentalized structure form a compartmentalized structure There are two types of compartments There are two types of compartments [[Red PulpRed Pulp and and White PulpWhite Pulp] ]
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Spleen Spleen bull Red Pulp-Red Pulp- Network of sinusoids populated with Network of sinusoids populated with
macrophages and numerous erythrocytes Site macrophages and numerous erythrocytes Site where old RBCs are destroyed and removed where old RBCs are destroyed and removed
bull White Pulp-White Pulp- Surrounds the splenic arteries Surrounds the splenic arteries forming a periarteriolar lymphoid sheath (PALS) forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes populated mainly by T lymphocytes
bull Clusters of B lymphocytes in the White Pulp form Clusters of B lymphocytes in the White Pulp form primary folliclesprimary follicles occupying a more peripheral occupying a more peripheral positionposition
bull Upon antigenic challenge these primary follicles Upon antigenic challenge these primary follicles develop into characteristic develop into characteristic secondary folliclessecondary follicles containing containing germinal centersgerminal centers
bull The spleen is The spleen is NOT supplied by afferent lymphaticsNOT supplied by afferent lymphatics
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Functions of the SpleenFunctions of the Spleenbull The spleen functions both as immune and The spleen functions both as immune and
hematopoietic systemshematopoietic systemsThe The immune functions include immune functions include
bull proliferation of lymphocytes proliferation of lymphocytes bull production of humoral antibodies production of humoral antibodies bull removal of macromolecular antigens from the blood removal of macromolecular antigens from the blood
The hematopoietic functions includeThe hematopoietic functions includebull formation of blood cells in fetal life formation of blood cells in fetal life bull removal and destruction of senile damaged and removal and destruction of senile damaged and
abnormal RBCs and platelets abnormal RBCs and platelets bull retrieval of the iron from hemoglobin retrieval of the iron from hemoglobin bull storage of blood in some species (not humans) storage of blood in some species (not humans)
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Lymphoid tissuesLymphoid tissues
bull Clumps of lymphoid tissue are Clumps of lymphoid tissue are found in many parts of the body found in many parts of the body especially in the linings of the especially in the linings of the digestive tract and the airways and digestive tract and the airways and lungsmdashterritories that serve as lungsmdashterritories that serve as gateways to the body These gateways to the body These tissues include the tissues include the tonsilstonsils adenoidsadenoids and and appendixappendix
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Peyers patchesPeyers patchesPeyers patches are areas of lymphoid Peyers patches are areas of lymphoid
tissue located in the wall of the intestine tissue located in the wall of the intestine and in some mammalian species such as and in some mammalian species such as sheep cattle and rabbitssheep cattle and rabbits
Peyers patches have a function similar to Peyers patches have a function similar to the bursa of fabricius of birds and bone the bursa of fabricius of birds and bone marrow of other mammals marrow of other mammals B cell B cell differentiation and maturationdifferentiation and maturation
bull Actually Two types of Peyers patches Actually Two types of Peyers patches seem to occur one with primary lymphoid seem to occur one with primary lymphoid function and another with secondary function and another with secondary lymphoid function lymphoid function
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Functions of lymphatic organsFunctions of lymphatic organs
11 GenerateGenerate immuno-competant immuno-competant lymphocyteslymphocytes
22 Concentrate antigensConcentrate antigens into lymphoid into lymphoid organsorgans
33 Circulate lymphocytesCirculate lymphocytes through through lymphoid organs exposing antigen lymphoid organs exposing antigen to a variety of lymphocytesto a variety of lymphocytes
44 Deliver antibodiesDeliver antibodies and effector T and effector T cells to the blood and tissuescells to the blood and tissues
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Kinds of Adaptive Kinds of Adaptive immunityimmunity
bullAdaptive immune responses Adaptive immune responses are actually reactions of the are actually reactions of the immune system to immune system to antigensantigens
bull There are two types of There are two types of adaptive immune responsesadaptive immune responses
bull Humoral and cell Humoral and cell mediatedmediated
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Adaptive Humoral immunityAdaptive Humoral immunity
bull During humoral immune responsesDuring humoral immune responses proteinsproteins called called antibodiesantibodies destroy destroy antigens appear in the blood and other antigens appear in the blood and other body fluids body fluids
bull Humoral immune responses resist invaders Humoral immune responses resist invaders that act outside of cells such as bacteria that act outside of cells such as bacteria and and toxinstoxins (poisonous substances produced (poisonous substances produced by living organisms) by living organisms)
bull Humoral immune responses can also Humoral immune responses can also prevent viruses from entering cellsprevent viruses from entering cells
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Adaptive cellular immunityAdaptive cellular immunity
bull During During cell-mediated immune responsescell-mediated immune responses cells that can destroy other cells that are cells that can destroy other cells that are either infected with or producing a specific either infected with or producing a specific antigen antigen
bull Cell-mediated immune responses resist Cell-mediated immune responses resist invaders that reproduce within the body invaders that reproduce within the body cells such as virusescells such as viruses
bull Cell-mediated responses may also destroy Cell-mediated responses may also destroy cells making cells making mutatedmutated (changed) forms of (changed) forms of normal molecules as in some cancersnormal molecules as in some cancers
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
Immunity is a coordinated effort Immunity is a coordinated effort by the bodyby the body
bull bull It was previously believed that the immune It was previously believed that the immune system functioned independently in the bodysystem functioned independently in the body
bull Itrsquos now known that there are several links Itrsquos now known that there are several links between the immune nervous and endocrine between the immune nervous and endocrine systemssystems
bull Certain immune responses trigger endocrine Certain immune responses trigger endocrine ampor nervous activityampor nervous activity
bull Lymphocytes amp macrophages are responsive to Lymphocytes amp macrophages are responsive to signals from the nervous system and certain signals from the nervous system and certain endocrine glandsendocrine glands
bull Therefore immunity is the job of the entire Therefore immunity is the job of the entire body not just one systembody not just one system
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
About the presenterAbout the presenterbull DrBVictor is a highly experienced postgraduate DrBVictor is a highly experienced postgraduate
biology teacher recently retired from the reputed biology teacher recently retired from the reputed educational institution St Xavierrsquo s College educational institution St Xavierrsquo s College Palayamkottai India-627001Presently HOD of Biotech Palayamkottai India-627001Presently HOD of Biotech at Annai Velankanni college Tholayavattam K K Distat Annai Velankanni college Tholayavattam K K Dist
bull He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St Xavierrsquos collegeexaminations of St Xavierrsquos college
bull He has more than 32 years of teaching and research He has more than 32 years of teaching and research experience and has guided more than 12 Ph D experience and has guided more than 12 Ph D scholarsscholars
bull He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate studentsgraduate and post graduate students
bull Send your comments to bonfiliusvictorgmailcomSend your comments to bonfiliusvictorgmailcom
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