Presented byPresented by

Dr. B. Victor, Dr. B. Victor,

St. Xavier’s College,St. Xavier’s College,

Palayamkottai-Palayamkottai-627002,India.627002,India.

Leucocytes are the effectorsLeucocytes are the effectorsof the immune system.of the immune system.

There are five types:There are five types:• NeutrophilsNeutrophils• EosinophilsEosinophils• BasophilsBasophils• MonocytesMonocytes• Lymphocytes - Two Types:Lymphocytes - Two Types:

• • B-cell lymphocytesB-cell lymphocytes• • T-cell lymphocytesT-cell lymphocytes

Blood cell categoriesBlood cell categoriesFormed elements

of the blood

Nucleated cellsNon-nucleated

cells

Leucocytes Erythrocytes Thromphocytes

Polymorphonuclear cells

EosinophilsNeutrophilsBasophils

MonocytesLymphocytes

Natural killer cells

There are two main lineages that There are two main lineages that derived from the hemopoietic stem derived from the hemopoietic stem

cell:cell:1. the lymphoid lineage1. the lymphoid lineage

T lymphocytes (T cells)T lymphocytes (T cells)B lymphocytes (B cells)B lymphocytes (B cells)Natural killer cells (NK cells)Natural killer cells (NK cells)

2. the myeloid lineage2. the myeloid lineageMonocytes, macrophagesMonocytes, macrophagesLangerhans cells, dendritic cellsLangerhans cells, dendritic cellsMegakaryocytesMegakaryocytesGranulocytes (eosinophils, neutrophils, Granulocytes (eosinophils, neutrophils, basophils)basophils)

Sub-categories of Sub-categories of LeucocytesLeucocytes

Leucocytes

Granulocytes(Polymorphonuclear

cells)

Agranulocytes(Mononuclear cells)

EosinophilsNeutrophilsBasophils

MonocytesLymphocytes

Natural killer cells

The agranulocytesThe agranulocytes::

They have a clear cytoplasm. They have a clear cytoplasm. Also known as mononuclear leukocytes. Also known as mononuclear leukocytes. These are the These are the Monocytes (4%) Monocytes (4%) Lymphocytes (24%). Lymphocytes (24%). The tissue macrophages, which are The tissue macrophages, which are active phagocytes, are probably derived active phagocytes, are probably derived from the monocytes, and have become from the monocytes, and have become resident in connective tissueresident in connective tissue

The granulocytes:The granulocytes:

They contain abundant granules in their They contain abundant granules in their cytoplasm. They are also known as cytoplasm. They are also known as polymorphonuclear leukocytes. polymorphonuclear leukocytes. (PMNs)(PMNs), , because of their lobed nuclei. because of their lobed nuclei.

Granulocytes are identified as different Granulocytes are identified as different types, based on their staining characteristics types, based on their staining characteristics with certain dyes. with certain dyes.

Neutrophils (72% of white cells), Neutrophils (72% of white cells),

Eosinophils (1.5%), Eosinophils (1.5%),

Basophils (0.5%). Basophils (0.5%).

Kinds of GranulocytesKinds of Granulocytes• Neutrophils Neutrophils

– Phagocytic as well as granulocytic, Phagocytic as well as granulocytic, neutrophils use granulocytic chemicals to neutrophils use granulocytic chemicals to destroy microorganisms which they ingest. destroy microorganisms which they ingest.

• Eosinophils Eosinophils – Eosinophils release granulocytic chemicals Eosinophils release granulocytic chemicals

into surrounding tissues, to destroy nearby into surrounding tissues, to destroy nearby infectious agents. infectious agents.

• Basophils Basophils – Like eosinophils, basophils release Like eosinophils, basophils release

granulocytic chemicals, to destroy nearby granulocytic chemicals, to destroy nearby microorganisms and stimulate the microorganisms and stimulate the inflammatory response. inflammatory response.

Granulocytes & AgranulocytesGranulocytes & Agranulocytes

Role of Granulocytes Role of Granulocytes

These cells are predominantly These cells are predominantly important in the removal of important in the removal of bacteria and parasites from the bacteria and parasites from the body. body.

They engulf these foreign bodies They engulf these foreign bodies and degrade them using their and degrade them using their powerful enzymes. powerful enzymes.

NNeutrophileutrophil

multi-lobed nucleus.multi-lobed nucleus.50-70% of circulating WBC (higher numbers 50-70% of circulating WBC (higher numbers suggestive of bacterial infection).suggestive of bacterial infection).The fine granules stain poorly with acidic The fine granules stain poorly with acidic and basic dyes neutrophil. and basic dyes neutrophil. Primary granules electron dense - contain Primary granules electron dense - contain bactericidal enzymes bactericidal enzymes – Lysozyme, myeloperoxidase; neutral Lysozyme, myeloperoxidase; neutral

proteases (i.e. elastase); and acid proteases (i.e. elastase); and acid hydrolases (B-glucoronidase hydrolases (B-glucoronidase

– Secondary granules – smaller, not Secondary granules – smaller, not electron dense.electron dense.

– lysozyme, collagenase and lactoferrin and lysozyme, collagenase and lactoferrin and cathepsin B). cathepsin B).

NeutrophilNeutrophil

• Neutrophils are Neutrophils are highly mobile highly mobile phagocytes.phagocytes.

• That travel around That travel around

in the blood & in the blood & engulf and destroy engulf and destroy unwanted unwanted material.material.

Role of NRole of Neutrophilseutrophils

Phagocytosis and killing of ingested Phagocytosis and killing of ingested microorganisms.microorganisms.The phagosome fuses with granules to The phagosome fuses with granules to destroy internalized bacteria, odestroy internalized bacteria, oxygen xygen dependent dependent respiratory burst.respiratory burst.DO NOT function as APCs.DO NOT function as APCs. Neutrophils are the 1st cells to arrive. A Neutrophils are the 1st cells to arrive. A number of substances produced during number of substances produced during an inflammatory response recruit an inflammatory response recruit neutrophils to a site of inflammation. neutrophils to a site of inflammation.

BasophilBasophil

( represent <1% of circulating WBC) ( represent <1% of circulating WBC) Lobed nucleus--more variable, large coarse Lobed nucleus--more variable, large coarse granules stain blue with granules stain blue with basic dye basic dye methylene bluemethylene blue.. They play a major role in the allergic They play a major role in the allergic response when they release their granules response when they release their granules (containing histamine, serotonin, heparin, (containing histamine, serotonin, heparin, prostaglandin, etc into the bloodstream prostaglandin, etc into the bloodstream following exposure to specific allergens). following exposure to specific allergens). Basophils bear Fc receptors for IgE  Basophils bear Fc receptors for IgE  When an individual is exposed to an When an individual is exposed to an allergen, allergen specific IgE is produced. allergen, allergen specific IgE is produced. This IgE binds to the surface of basophilsThis IgE binds to the surface of basophils

BasophilBasophil

• Basophils release Basophils release histamine and histamine and heparin.heparin.

• Important in Important in allergic allergic responses.responses.

EosinophilEosinophil

(represent 1-3% of circulating WBCs) (represent 1-3% of circulating WBCs) Possess a bi-lobed nucleus and a heavily Possess a bi-lobed nucleus and a heavily granulated cytoplasm. granulated cytoplasm. Granules stain orange/red with the acidic Granules stain orange/red with the acidic dye Eosin Y.dye Eosin Y.Somewhat phagocytic but Somewhat phagocytic but DO NOT act as DO NOT act as APCs.APCs. The major role of the eosinophil is The major role of the eosinophil is believed to be against parasites, believed to be against parasites, particularly parasitic worms. particularly parasitic worms.

EosinophilEosinophil

• Eosinophils Eosinophils secrete chemicals secrete chemicals that fight that fight parasites parasites (worms).(worms).

Immunocytic systemImmunocytic system

Immunocyticsystem

Cell mediated immunity

HumouralImmunity

Production of Lymphokines

Production of Antibodies

T-LymphocytesB-Lymphocytes(Plasma cells)

LymphopoiesisLymphopoiesis•The process of lymphopoiesis The process of lymphopoiesis

(lymphocyte origination and (lymphocyte origination and differentiation into functional differentiation into functional effector cells) begins in the effector cells) begins in the yolk sac and continues later in yolk sac and continues later in life in the thymus gland, liver, life in the thymus gland, liver, spleen, and finally the bone spleen, and finally the bone marrow. marrow.

Origin of cells of the immune Origin of cells of the immune system system 

LymphocytesLymphocytes

Lymphocytes are the main actors of the Lymphocytes are the main actors of the immunocytic system. immunocytic system. responsible for the specific immune responsible for the specific immune response. response. Represent 20-40% of circulating WBC in Represent 20-40% of circulating WBC in blood extravasate and enter the tissues – blood extravasate and enter the tissues – return 99% of cells in lymph return 99% of cells in lymph small 6µm, contain a single nucleus, little small 6µm, contain a single nucleus, little visible cytoplasm around their nucleus. visible cytoplasm around their nucleus. T lymphocytes and B lymphocytes and T lymphocytes and B lymphocytes and natural killer cells. natural killer cells.

Lymphocytes

Lymphocytes

T-Lymphocytes B-Lymphocytes

T-helper cellsT-suppressor cellsT-cytotoxic cells

T-delayed hypersensitivity cells

Plasma cells B-memory cells

T and B-LymphocytesT and B-Lymphocytes T and B lymphocytes are small, motile, T and B lymphocytes are small, motile, nonphagocytic cells which cannot be nonphagocytic cells which cannot be distinguished from each other morphologically. distinguished from each other morphologically. Once stimulated with antigen enlarges 15µm Once stimulated with antigen enlarges 15µm into a blast cell. Lymphoblasts further into a blast cell. Lymphoblasts further differentiate into effector cells or memory cells.  differentiate into effector cells or memory cells.  [Plasma cells, T-helper cells, T-cytotoxic cells]. [Plasma cells, T-helper cells, T-cytotoxic cells]. The memory cells are long-lived cells that reside The memory cells are long-lived cells that reside in the Go phase of the cell cycle until activated in the Go phase of the cell cycle until activated by a secondary encounter with antigen. by a secondary encounter with antigen. Different lineages or different maturational Different lineages or different maturational stages of lymphocytes can be distinguished by stages of lymphocytes can be distinguished by their expression of membrane CD molecules their expression of membrane CD molecules ((Cluster of Differentiation (CD)Cluster of Differentiation (CD)

T and B lymphocytesT and B lymphocytes

T cells are chiefly responsible for T cells are chiefly responsible for Cell mediated Cell mediated immunityimmunity B cells are primarily responsible for B cells are primarily responsible for Humoral Humoral mediated immunitymediated immunity (relating to antibodies). (relating to antibodies). T cells are named such because these T cells are named such because these lymphocytes mature in the thymus; lymphocytes mature in the thymus; B cells, named for the Bursa of fabricius in B cells, named for the Bursa of fabricius in which they mature in bird species, are thought which they mature in bird species, are thought to to mature in the bone marrow in humans.mature in the bone marrow in humans.In the presence of an antigen, B cells can In the presence of an antigen, B cells can become much more metabolicallybecome much more metabolically active and active and differentiate into plasma cells, which secrete differentiate into plasma cells, which secrete large quantities of antibodies.large quantities of antibodies.

T Lymphocytes (T-cells ) attack T Lymphocytes (T-cells ) attack the invaders directlythe invaders directly

T cells are antigen specific. They acquire T cells are antigen specific. They acquire receptors for this specificity in the thymus . receptors for this specificity in the thymus . Some of them (CD4+) secrete lymphokines Some of them (CD4+) secrete lymphokines which act on other cells involved in the which act on other cells involved in the immune response. immune response. Others (CD8+, cytotoxic) are able to cause Others (CD8+, cytotoxic) are able to cause lysis of infected cells. lysis of infected cells.

Human T-lymphocyte Human T-lymphocyte (SEM x12,080).(SEM x12,080).

T Lymphocytes (T Cells)T Lymphocytes (T Cells)

• Helper T cells Helper T cells – Helper T cells are responsible for activating and Helper T cells are responsible for activating and

orchestrating the response against an invading orchestrating the response against an invading organism. organism.

• Cytotoxic (or Killer) T CellsCytotoxic (or Killer) T Cells – Killer T cells are responsible for destruction of Killer T cells are responsible for destruction of

virus-infected or malignant (cancerous) body virus-infected or malignant (cancerous) body cells. cells.

• Suppressor T CellsSuppressor T Cells – Suppressor T cells are responsible for turning Suppressor T cells are responsible for turning

off the immune response after an infection has off the immune response after an infection has been cleared. been cleared.

T LymphocytesT Lymphocytes

Role of T-lymphocytesRole of T-lymphocytes

• T- helper cells interact with B- lymphocytes T- helper cells interact with B- lymphocytes and help them to divide, differentiate and and help them to divide, differentiate and antibodies.antibodies.

• T- helper cells interact with mononuclear T- helper cells interact with mononuclear phagocytes and help them destroy phagocytes and help them destroy pathogens.pathogens.

• T- cytotoxic cells are responsible for the T- cytotoxic cells are responsible for the destruction of host cells infected with viruses destruction of host cells infected with viruses or other intracellular pathogens.or other intracellular pathogens.

B lymphocytesB lymphocytes

– B lymphocytes are responsible for B lymphocytes are responsible for producing antibodies, specialized proteins producing antibodies, specialized proteins which react against foreign invaders. which react against foreign invaders.

B cells mature into plasma cells B cells mature into plasma cells that produce antibodies.that produce antibodies.

B cells perform antibody B cells perform antibody mediated immunity.mediated immunity.

• B lymphocytes have receptors on its surface to B lymphocytes have receptors on its surface to recognize one unique antigen.recognize one unique antigen.

• Antigens stimulate B cells to convert into Antigens stimulate B cells to convert into plasma cells that produce antibodies (specific to plasma cells that produce antibodies (specific to that antigen).that antigen).

• A plasma cell produces antibody molecules that A plasma cell produces antibody molecules that can combine with a specific kind of antigen (like can combine with a specific kind of antigen (like a lock & key).a lock & key).

• All antibodies eventually enter the blood or All antibodies eventually enter the blood or lymph.lymph.

• B-cells specialize in fighting bacterial invaders.B-cells specialize in fighting bacterial invaders.

Plasma CellsPlasma Cells

1. 1. B-B-cells cells on stimulation, grow, proliferate on stimulation, grow, proliferate and differentiate into plasma cells.and differentiate into plasma cells.

2. Plasma cells have a nucleus with chromatin 2. Plasma cells have a nucleus with chromatin arranged in a wheel-spoke pattern and an arranged in a wheel-spoke pattern and an abundant, basophilic cytoplasm.abundant, basophilic cytoplasm.

3. Their 3. Their extensive extensive granular endoplasmic granular endoplasmic reticulumreticulum produces immunoglobulins. produces immunoglobulins.

4. After completing secretion, most plasma 4. After completing secretion, most plasma cells die; however, some may survive for cells die; however, some may survive for months or even years and serve as months or even years and serve as memory memory cellscells..

Plasma CellPlasma Cell

Antibodies (Immunoglubulins)Antibodies (Immunoglubulins)Proteins produced by B cells to interact with Proteins produced by B cells to interact with and incapacitate and/or eliminate specific and incapacitate and/or eliminate specific foreign invadersforeign invaders – Antibodies can work in one of several waysAntibodies can work in one of several ways::

Antitoxin Effect-Antitoxin Effect- Binding of antibody to a Binding of antibody to a bacterial toxin can inactivate the toxin directly. bacterial toxin can inactivate the toxin directly. OpsonizationOpsonization-- Microbes coated with antibody Microbes coated with antibody are a more attractive target for phagocytic cells are a more attractive target for phagocytic cells such as macrophages such as macrophages Complement Activation-Complement Activation- Binding of antibody Binding of antibody to an invading microbe can activate the to an invading microbe can activate the complement cascade resulting in destruction of complement cascade resulting in destruction of the microbe the microbe Virus Neutralization-Virus Neutralization- Binding of antibody to a Binding of antibody to a virus can block the virus from entering body cells. virus can block the virus from entering body cells. Antibody-Dependent Cell-Mediated Antibody-Dependent Cell-Mediated Cytotoxicity-Cytotoxicity- Binding of antibody to cells makes Binding of antibody to cells makes cells susceptible to destruction by cytotoxic cells susceptible to destruction by cytotoxic (killer) immune cells. (killer) immune cells.

Natural Killer CellsNatural Killer Cells

• Natural killer cells (lymphocyte-like cells) Natural killer cells (lymphocyte-like cells) attack & destroy virus-infected cells and attack & destroy virus-infected cells and cancer cells on first exposure to them.cancer cells on first exposure to them.

– – They lyse (rupture) cell membranes upon They lyse (rupture) cell membranes upon first exposure to these cells.first exposure to these cells.

– – NK cells provide an immediate, NK cells provide an immediate, nonspecific defense.nonspecific defense.

• They act to slow the spread of viruses & They act to slow the spread of viruses & cancer cells until the more specific cancer cells until the more specific adaptive immune cells can be mobilized.adaptive immune cells can be mobilized.

Natural Killer CellsNatural Killer Cells

Natural killer cell, Killer cell and Natural killer cell, Killer cell and cytotoxic T lymphocytescytotoxic T lymphocytes

B cell-T cell interactionB cell-T cell interaction

B cell-T cell interactionB cell-T cell interaction

B cell receptor (BCR)B cell receptor (BCR)and T cell receptor (TCRand T cell receptor (TCR

• Each B cell and T cell is specific for Each B cell and T cell is specific for a particular antigen. This means a particular antigen. This means that each is able to bind to a that each is able to bind to a particular molecular structure. particular molecular structure.

• The specificity of binding resides in The specificity of binding resides in a receptor for antigen: a receptor for antigen:

• the B cell receptor (BCR)the B cell receptor (BCR)• the T cell receptor (TCR).the T cell receptor (TCR).

Both BCRs and TCRs share these Both BCRs and TCRs share these propertiesproperties

• They are integral membrane proteins. They are integral membrane proteins. • They are present in thousands of identical They are present in thousands of identical

copies exposed at the cell surface. copies exposed at the cell surface. • They are made before the cell ever encounters They are made before the cell ever encounters

an antigen. an antigen. • They are encoded by genes assembled by the They are encoded by genes assembled by the

recombination of segments of DNA. recombination of segments of DNA. • They have a unique binding site. They have a unique binding site. • This site binds to a portion of the antigen This site binds to a portion of the antigen

called an antigenic determinant or epitope. called an antigenic determinant or epitope. • The binding depends on complementarity of The binding depends on complementarity of

the surface of the receptor and the surface of the surface of the receptor and the surface of the epitope. the epitope.

• The binding occurs by non- covalent forces The binding occurs by non- covalent forces (again, like an enzyme binding to its (again, like an enzyme binding to its substrate). substrate).

BCRs and TCRs differ in:BCRs and TCRs differ in:

• their structure; their structure; • the genes that encode them; the genes that encode them; • the type of epitope to which they the type of epitope to which they

bind.bind.

Antigen receptors expressed as Antigen receptors expressed as transmembrane molecules on B and Ttransmembrane molecules on B and T

lymphocyteslymphocytes

Other cells of the immune Other cells of the immune systemsystem• Natural Killer CellsNatural Killer Cells

• Natural killer cells are responsible for non-specific Natural killer cells are responsible for non-specific destruction of virus-infected or malignant body cells. destruction of virus-infected or malignant body cells.

• Monocytes Monocytes • Monocytes are large white blood cells which circulate Monocytes are large white blood cells which circulate

in the blood, then migrate into tissues to mature into in the blood, then migrate into tissues to mature into macrophages. macrophages.

• MacrophagesMacrophages • Macrophages are phagocytic cells responsible for Macrophages are phagocytic cells responsible for

engulfing and digesting foreign invaders.  engulfing and digesting foreign invaders.  Examples of tissue-specific macrophages include: Examples of tissue-specific macrophages include: – Alveolar Macrophages (in the lungs) Alveolar Macrophages (in the lungs) – Mesangial Macrophages (in the kidneysMesangial Macrophages (in the kidneys) ) – Microglial Cells (in the brain) Microglial Cells (in the brain) – Kupffer Cells (in the liver) Kupffer Cells (in the liver)

MonocytesMonocytes

Monocytes are Monocytes are produced by the bone produced by the bone marrowmarrow from haematopoietic stem cells from haematopoietic stem cells precursors.precursors.

They They circulate in the blood streamcirculate in the blood stream for for about one to three days and then typically about one to three days and then typically move into tissues throughout the body. move into tissues throughout the body.

In the tissues monocytes In the tissues monocytes mature into mature into different types of macrophagesdifferent types of macrophages at at different anatomical locations.different anatomical locations.

MonocyteMonocyteMonocytes can Monocytes can perform perform phagocytosisphagocytosis using using intermediary (intermediary (opsonisingopsonising) ) proteins such as antibodies or proteins such as antibodies or complement that coat the complement that coat the pathogen.pathogen.They bind to the microbe They bind to the microbe directly via pattern-directly via pattern-recognition receptors that recognition receptors that recognize pathogens. recognize pathogens. Monocytes are also capable Monocytes are also capable of killing infected host cells of killing infected host cells via antibody, termed via antibody, termed antibody-mediated cellular antibody-mediated cellular cytotoxicity. cytotoxicity.

Dendritic CellsDendritic Cells

originate in the bone originate in the bone marrowmarrowfunction as function as antigen antigen presenting cells (APC).presenting cells (APC). found in the structural found in the structural compartment of the compartment of the lymphoid organslymphoid organsfound in the bloodstream found in the bloodstream and other tissues of the and other tissues of the bodybodycapture antigen or bring it capture antigen or bring it to the lymphoid organs to the lymphoid organs where an immune response where an immune response is initiated. is initiated.

Dendritic CellsDendritic Cells

• Stationed in skinStationed in skin• Particularly Particularly

susceptible to susceptible to infection by virusesinfection by viruses

• Present internally-Present internally-produced antigens produced antigens on MHC Ion MHC I

Antigen Presenting cell (APC)Antigen Presenting cell (APC)

Phagocytes and Their Phagocytes and Their RelativesRelatives

Monocytes and MacrophagesMonocytes and Macrophagesrepresent 5-8% of WBCsrepresent 5-8% of WBCsmonocytes enter the tissues through the process of extravastion. monocytes enter the tissues through the process of extravastion. Changes which occur during this transition:Changes which occur during this transition: Cells enlarge [5-10x] Cells enlarge [5-10x] intracellular organelles increase in number and complexity intracellular organelles increase in number and complexity cells acquire increased phagocytic ability cells acquire increased phagocytic ability increased secretion of many soluble factors increased secretion of many soluble factors

• Macrophages play the following important roles: Macrophages play the following important roles: 1) phagocytosis 1) phagocytosis 2) antimicrobial activity 2) antimicrobial activity 3) secretion of soluble factors 3) secretion of soluble factors

• Macrophages are activated by a variety of stimuli in the course of an Macrophages are activated by a variety of stimuli in the course of an immune response.immune response. - One of the earliest activating signals comes from chemokines. - One of the earliest activating signals comes from chemokines. - Phagocyotosis itself is an important activating stimulus. - Phagocyotosis itself is an important activating stimulus. - Macrophages are further activated by cytokines secreted by - Macrophages are further activated by cytokines secreted by T helper T helper cells [IFN-gamma] cells [IFN-gamma] - and by mediators of the inflammatory response - and by mediators of the inflammatory response - and by various microbial products (such as LPS) - and by various microbial products (such as LPS)

MacrophagesMacrophages• These cells are derived These cells are derived

from the bone marrow from the bone marrow and have a variety of and have a variety of functions in the immune functions in the immune response: response: phagocytosis phagocytosis secretion of cytokinessecretion of cytokines

• The cells performing The cells performing these various functions these various functions have differing have differing microscopic microscopic appearances but they appearances but they are grouped together as are grouped together as the the mononuclear mononuclear phagocytic system.phagocytic system.

PhagocytesPhagocytes

Phagocytes are large white cells Phagocytes are large white cells that can swallow and digest that can swallow and digest microbes and other foreign microbes and other foreign particles. particles. MonocytesMonocytes are are phagocytes that circulate in the phagocytes that circulate in the blood.blood.When monocytes migrate into When monocytes migrate into tissues, they develop into tissues, they develop into macrophagesmacrophages..Specialized types of macrophages Specialized types of macrophages can be found in many organs, can be found in many organs, including lungs, kidneys, brain, including lungs, kidneys, brain, and liver.and liver.

Macrophages play many roles.Macrophages play many roles.

As scavengers, they rid the body of As scavengers, they rid the body of worn-out cells and other debris. –worn-out cells and other debris. –They display bits of foreign antigen in a They display bits of foreign antigen in a way that draws the attention of way that draws the attention of matching lymphocytes. matching lymphocytes. They churn out an amazing variety of They churn out an amazing variety of powerful chemical signals, known as powerful chemical signals, known as monokinesmonokines, which are vital to the , which are vital to the immune responses.immune responses.

Macrophage attacking Macrophage attacking E.coliE.coli (SEM x8,800(SEM x8,800).).

Normal anti-bacterial Normal anti-bacterial actionaction

1. PHAGOCYTIC CELL ENGAGES MICROBE

2. PHAGOCYTOSIS OF THE MICROBE

3. DESTRUCTION OF THE MICROBE

Mast cellMast cell

A mast cell (or A mast cell (or mastocytemastocyte) is a ) is a resident resident cell of connective tissuecell of connective tissue that contains that contains many granules rich in histamine and many granules rich in histamine and heparin. heparin.

Although best known for their role in Although best known for their role in allergy and anaphylaxis, mast cells play allergy and anaphylaxis, mast cells play an important protective role as well, an important protective role as well, being intimately involved in being intimately involved in wound wound healing and defense against pathogens.healing and defense against pathogens.

Mast cellMast cellThe The mast cell mast cell is a is a twin of the basophil, twin of the basophil, except that it is not except that it is not a blood cell. a blood cell. it is found in the it is found in the lungs, skin, tongue, lungs, skin, tongue, and linings of the and linings of the nose and intestinal nose and intestinal tract, where it is tract, where it is responsible for the responsible for the symptoms of allergy.symptoms of allergy.

Mast cellsMast cells Mast cells are released from the bone marrow as Mast cells are released from the bone marrow as undifferentiated precursor cells and do not undifferentiated precursor cells and do not differentiate until they enter the tissues (skin, differentiate until they enter the tissues (skin, connective tissue, mucosal epithelium, etc.) connective tissue, mucosal epithelium, etc.) Morphology and function similar to circulating Morphology and function similar to circulating basophils - but clearly derived from a distinct cell basophils - but clearly derived from a distinct cell lineage. lineage. Mast cells bear Fc receptors for IgE (Mast cells bear Fc receptors for IgE (FcRs)FcRs) and and contain large numbers of cytoplasmic granules which contain large numbers of cytoplasmic granules which also play a very important role in the allergic also play a very important role in the allergic response. response. They produce a variety of cytokines They produce a variety of cytokines TNF is produced and stored within the cytoplasm of TNF is produced and stored within the cytoplasm of the mast cell, and it can be released quickly the mast cell, and it can be released quickly following mast cell activation.following mast cell activation.

About the presenterAbout the presenter• Dr.B.Victor is a highly experienced postgraduate Dr.B.Victor is a highly experienced postgraduate

biology teacher, recently retired from the reputed biology teacher, recently retired from the reputed educational institution St. Xavier’ s College, educational institution St. Xavier’ s College, Palayamkottai, India-627001.Presently HOD of Biotech Palayamkottai, India-627001.Presently HOD of Biotech at Annai Velankanni college, Tholayavattam. K .K Distat Annai Velankanni college, Tholayavattam. K .K Dist

• He was the dean of sciences and assistant controller of He was the dean of sciences and assistant controller of examinations of St. Xavier’s college.examinations of St. Xavier’s college.

• 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 scholars.scholars.

• He has taught Immunology and biochemistry to He has taught Immunology and biochemistry to graduate and post graduate students.graduate and post graduate students.

• Send your comments to : bonfiliusvictor@gmail.comSend your comments to : bonfiliusvictor@gmail.com