The Lymphatic The Lymphatic System and System and ImmunityImmunity

FunctionsFunctions

Production, maintenance, and Production, maintenance, and distribution of lymphocytes that distribution of lymphocytes that provide defense against infections provide defense against infections and other environmental hazardsand other environmental hazards

What is lymph?What is lymph?

A fluid that resembles plasma but A fluid that resembles plasma but contains a much lower concentration contains a much lower concentration of suspended proteinsof suspended proteins

Lymphatic VesselsLymphatic Vessels Carry lymph from peripheral tissues to Carry lymph from peripheral tissues to

the venous systemthe venous system Superficial and deep lymphatics converge Superficial and deep lymphatics converge

to form lymphatic trunks which empty to form lymphatic trunks which empty into two large collecting vessels: the into two large collecting vessels: the thoracic duct and the right lymphatic thoracic duct and the right lymphatic ductduct

Blockage of the lymphatic drainage Blockage of the lymphatic drainage produces produces lymphedemalymphedema (condition in (condition in which interstitial fluids accumulate and which interstitial fluids accumulate and the limb gradually becomes swollen and the limb gradually becomes swollen and grossly distended)grossly distended)

LymphocytesLymphocytes Account for 20-30 percent of the Account for 20-30 percent of the

circulating leukocyte population; circulating leukocyte population; produced in bone marrow and lymphoid produced in bone marrow and lymphoid tissuestissues

FYI: body has 10FYI: body has 1012 12 with a combined weight with a combined weight of more than a kgof more than a kg

T-cells (thymus-dependent)T-cells (thymus-dependent) CytotoxicCytotoxic – attack foreign cells or body cells – attack foreign cells or body cells

infected by viruses infected by viruses HelperHelper – stimulate the activation and function – stimulate the activation and function

of both T cells and B cellsof both T cells and B cells SuppressorSuppressor – inhibit the activation and – inhibit the activation and

function of both T cells and B cellsfunction of both T cells and B cells

B cells (bone marrow-derived)B cells (bone marrow-derived) When stimulated, can differentiate into When stimulated, can differentiate into

plasma cells, which are responsible for plasma cells, which are responsible for the production and secretion of the production and secretion of antibodiesantibodies

NK cells (natural killer)NK cells (natural killer) Attack foreign cells, normal cells Attack foreign cells, normal cells

infected with viruses, and cancer cells infected with viruses, and cancer cells that appear in normal tissuesthat appear in normal tissues

Lymphoid TissuesLymphoid Tissues

MALT (mucosa-associated lymphoid MALT (mucosa-associated lymphoid tissue)tissue) Collection of lymphoid tissues linked Collection of lymphoid tissues linked

with the digestive systemwith the digestive system TonsilsTonsils

Large lymphoid nodules in the walls of Large lymphoid nodules in the walls of the pharynxthe pharynx

Lymphoid OrgansLymphoid Organs

Lymph nodesLymph nodes 1 mm to 25 mm1 mm to 25 mm Functions like a kitchen water filter, Functions like a kitchen water filter,

purifying lymph before it reaches the purifying lymph before it reaches the venous circulationvenous circulation

Fixed macrophages in the walls of the Fixed macrophages in the walls of the lymphatic sinuses engulf debris or lymphatic sinuses engulf debris or pathogens in lymph as it flows pastpathogens in lymph as it flows past

Provide an early-warning systemProvide an early-warning system

ThymusThymus Pink, grainy organ located in the Pink, grainy organ located in the

mediastinummediastinum Gradual decrease in size over lifetimeGradual decrease in size over lifetime Relation to disease in elderly?Relation to disease in elderly? Produce T-cellsProduce T-cells Produces thymosin which promotes the Produces thymosin which promotes the

development and maturation of development and maturation of lymphocyteslymphocytes

SpleenSpleen Removal of abnormal blood cells by Removal of abnormal blood cells by

phagocytosisphagocytosis Storage of iron recycled from rbcsStorage of iron recycled from rbcs Initiation of immune responses by B Initiation of immune responses by B

cells and T cells in response to antigens cells and T cells in response to antigens in circulating bloodin circulating blood

Nonspecific DefensesNonspecific Defenses

Physical barriersPhysical barriers EpitheliumEpithelium Secretions (mucus, acid)Secretions (mucus, acid) HairHair Sweat gland ductSweat gland duct

PhagocytesPhagocytes Remove cellular debrisRemove cellular debris Attack and remove microorganismsAttack and remove microorganisms Microphages and macrophagesMicrophages and macrophages

Immunological surveillanceImmunological surveillance Constant monitoring of normal tissues by Constant monitoring of normal tissues by

NK cellsNK cells

1.1. NK cell recognizes abnormal cell and NK cell recognizes abnormal cell and adheresadheres

2.2. Golgi apparatus aligns to face abnormal cellGolgi apparatus aligns to face abnormal cell

3.3. Perforins diffuse from NK cell to abnormal Perforins diffuse from NK cell to abnormal cellcell

4.4. Perforins create a network of pores in Perforins create a network of pores in abnormal cell membraneabnormal cell membrane

InterferonsInterferons Small proteins released by activated Small proteins released by activated

lymphocytes and macrophages and by lymphocytes and macrophages and by tissue cells infected with virusestissue cells infected with viruses

1.1. Binds to surface receptors on the cellBinds to surface receptors on the cell

2.2. Triggers the production of antiviral Triggers the production of antiviral proteins in the cytoplasmproteins in the cytoplasm

3.3. Interfere with viral replication inside Interfere with viral replication inside the cellthe cell

ComplementComplement Proteins that complement the action of Proteins that complement the action of

antibodiesantibodies Enhance the release of histamine by Enhance the release of histamine by

mast cellsmast cells Attract phagocytesAttract phagocytes Makes the target easier to engulfMakes the target easier to engulf Destruct target cell membranesDestruct target cell membranes

InflammationInflammation Produces local swelling, redness, heat, and painProduces local swelling, redness, heat, and pain Injury is temporarily repairedInjury is temporarily repaired Spread of pathogens away from the injury is slowedSpread of pathogens away from the injury is slowed Local, regional, and systemic defenses are mobilized Local, regional, and systemic defenses are mobilized

to overcome pathogens and facilitate permanent to overcome pathogens and facilitate permanent repairsrepairs

FeverFever Maintenance of body temperature greater than Maintenance of body temperature greater than

37.2°C (99°F)37.2°C (99°F) Pyrogens reset thermostatPyrogens reset thermostat Quicker mobilization of tissue defenses and an Quicker mobilization of tissue defenses and an

accelerated repair processaccelerated repair process

Specific DefensesSpecific Defenses

T cells are responsible for cell-T cells are responsible for cell-mediated immunitymediated immunity Defends against abnormal cells and Defends against abnormal cells and

pathogens inside cellspathogens inside cells B cells are responsible for antibody-B cells are responsible for antibody-

mediated immunitymediated immunity Defends against antigens and Defends against antigens and

pathogens in body fluidspathogens in body fluids

Forms of ImmunityForms of Immunity

Innate – genetically determinedInnate – genetically determined Acquired immunity – only when Acquired immunity – only when

exposed to antigenexposed to antigen Active – develops after exposure to Active – develops after exposure to

antigen antigen Natural (over time)Natural (over time) Induced (vaccine)Induced (vaccine)

Passive – produced by the transfer of Passive – produced by the transfer of antibodies from another source antibodies from another source Natural (breast milk)Natural (breast milk) Induced (antibodies against rabies virus)Induced (antibodies against rabies virus)

T-cells and Cell-mediated T-cells and Cell-mediated Immunity p.371Immunity p.371

Antigen-bearing agents enter tissues.Antigen-bearing agents enter tissues. An accessory cell phagocytizes the antigen-bearing An accessory cell phagocytizes the antigen-bearing

agent and lysosomes digest the agentagent and lysosomes digest the agent Antigens from the digested antigen-bearing agents Antigens from the digested antigen-bearing agents

are displayed on the surface membrane of the are displayed on the surface membrane of the accessory cellaccessory cell

Helper T cell becomes activated when it encounters a Helper T cell becomes activated when it encounters a displayed antigen that fits its antigen receptorsdisplayed antigen that fits its antigen receptors

Activated helper T cell releases cytokines when it Activated helper T cell releases cytokines when it encounters a B cell that has previously combined with encounters a B cell that has previously combined with an identical antigen-bearing agentan identical antigen-bearing agent

Cytokines stimulate the B cell to proliferateCytokines stimulate the B cell to proliferate Some differentiate into antibody-secreting plasma Some differentiate into antibody-secreting plasma

cellscells Antibodies combine with antigen-bearing agents, Antibodies combine with antigen-bearing agents,

helping to destroy themhelping to destroy them

B Cells and Antibody-B Cells and Antibody-Mediated Immunity p.372Mediated Immunity p.372

Antigen-bearing agents enter tissuesAntigen-bearing agents enter tissues B Cell becomes activated when it encounters B Cell becomes activated when it encounters

an antigen that fits its antigen receptorsan antigen that fits its antigen receptors Activated B cell proliferates, enlarging its Activated B cell proliferates, enlarging its

cloneclone Some of the newly formed B cells Some of the newly formed B cells

differentiate further to become plasma cellsdifferentiate further to become plasma cells Plasma cells synthesize and secrete Plasma cells synthesize and secrete

antibodies whose molecular structure is antibodies whose molecular structure is similar to the activated B cell’s antigen similar to the activated B cell’s antigen receptorsreceptors

Antibodies combine with antigen-bearing Antibodies combine with antigen-bearing agents, helping to destroy themagents, helping to destroy them

Types of AntibodiesTypes of Antibodies

A.k.a. immunoglobulinsA.k.a. immunoglobulins Soluble, globular proteinsSoluble, globular proteins IgGIgG – effective against bacteria, viruses, – effective against bacteria, viruses,

and toxinsand toxins IgA – found in exocrine gland secretions IgA – found in exocrine gland secretions

(breast milk, tears, nasal fluid, bile, urine)(breast milk, tears, nasal fluid, bile, urine) IgM – develops in response to contact with IgM – develops in response to contact with

certain antigens in foods or bacteriacertain antigens in foods or bacteria IgD – important in activating B cellsIgD – important in activating B cells IgE – associated with allergic reactionsIgE – associated with allergic reactions

Antibody ActionsAntibody Actions

Directly attack Directly attack antigensantigens

Active complement to Active complement to attack the antigensattack the antigens

Stimulate changes in Stimulate changes in local areas that help local areas that help prevent the spread of prevent the spread of pathogens or cells pathogens or cells bearing foreign bearing foreign antigensantigens

HIV Antibody testHIV Antibody test

Allergic ReactionsAllergic Reactions An immune attack against a nonharmful An immune attack against a nonharmful

substance, such as chocolatesubstance, such as chocolate Can damage tissuesCan damage tissues Antigens that trigger allergic responses are Antigens that trigger allergic responses are

called allergenscalled allergens Delayed-reaction allergyDelayed-reaction allergy – usually takes – usually takes

about 48 hrs to occur; results from repeated about 48 hrs to occur; results from repeated exposure of the skin to certain chemicals; exposure of the skin to certain chemicals; may affect anyonemay affect anyone

Immediate-reaction allergyImmediate-reaction allergy – occurs within – occurs within minutes after contact with allergen; affects minutes after contact with allergen; affects people who have an inherited tendency to people who have an inherited tendency to overproduce IgE antibodiesoverproduce IgE antibodies

Anaphylactic ShockAnaphylactic Shock Severe form of immediate-reaction allergy Severe form of immediate-reaction allergy

in which mast cells release allergy in which mast cells release allergy mediators throughout the bodymediators throughout the body

Entire body itches and breaks out in red Entire body itches and breaks out in red hiveshives

Vomiting and diarrhea may followVomiting and diarrhea may follow Face, tongue, and larynx begin to swell Face, tongue, and larynx begin to swell

and breathing becomes difficultand breathing becomes difficult Unless the person receives an injection of Unless the person receives an injection of

epinephrine he or she will lose epinephrine he or she will lose consciousness and may die within 5 consciousness and may die within 5 minutesminutes

Transplantation and Tissue Transplantation and Tissue RejectionRejection Recipient’s immune system may recognize the Recipient’s immune system may recognize the

donor’s cell surfaces as foreign and attempt to donor’s cell surfaces as foreign and attempt to destroy the transplanted tissue, causing destroy the transplanted tissue, causing tissue tissue rejection reactionrejection reaction

Immunosuppressive drugsImmunosuppressive drugs are used to reduce are used to reduce rejectionrejection

Suppresses formation of antibodies or production Suppresses formation of antibodies or production of T cellsof T cells

Can leave a recipient unprotected against Can leave a recipient unprotected against infectionsinfections

How long can donated organs last outside of body?How long can donated organs last outside of body? Heart: 3-5 hrsHeart: 3-5 hrs Liver: 10 hrsLiver: 10 hrs Kidney: 24-48 hrsKidney: 24-48 hrs

AutoimmunityAutoimmunity

Immune system fails to distinguish Immune system fails to distinguish self from nonself, producing self from nonself, producing autoantibodies autoantibodies and cytotoxic T cells and cytotoxic T cells that attack and damage the body’s that attack and damage the body’s tissues and organstissues and organs

Type I diabetes mellitus, rheumatoid Type I diabetes mellitus, rheumatoid arthritis, and systemic lupus arthritis, and systemic lupus erythematosuserythematosus

HIV/AIDSHIV/AIDS HIV is the virus that HIV is the virus that

leads to the disease leads to the disease AIDSAIDS

HIV finds and HIV finds and destroys a type of destroys a type of white blood cell (T white blood cell (T cells or CD4 cells)cells or CD4 cells)

Scientists identified Scientists identified a type of chimpanzee a type of chimpanzee in West Africa as the in West Africa as the source of HIV source of HIV infection in humans. infection in humans.

HIV was first identified in the HIV was first identified in the United States in 1981 United States in 1981

In 2006, an estimated 56,300 In 2006, an estimated 56,300 U.S. individuals were infected U.S. individuals were infected with HIV. with HIV.

about 1 million people in the about 1 million people in the United States are living with United States are living with HIV or AIDS HIV or AIDS

Transmitted byTransmitted by Having sex (anal, vaginal, or Having sex (anal, vaginal, or

oral) with someone infected oral) with someone infected with HIV with HIV

Sharing needles and syringes Sharing needles and syringes with someone infected with with someone infected with HIV HIV

Being exposed (fetus or Being exposed (fetus or infant) to HIV before or infant) to HIV before or during birth or through during birth or through breast feeding breast feeding

blood infected with HIV blood infected with HIV

not transmittednot transmitted through through shaking handsshaking hands hugginghugging casual kisscasual kiss toilet seattoilet seat drinking fountaindrinking fountain doorknobdoorknob dishesdishes drinking glassesdrinking glasses FoodFood PetsPets mosquitoesmosquitoes

Preventing TransmissionPreventing Transmission

Abstain from sex (do Abstain from sex (do not have oral, anal, or not have oral, anal, or vaginal sex) until you vaginal sex) until you are in a relationship are in a relationship with only one person, with only one person, are having sex with are having sex with only each other, and only each other, and each of you knows the each of you knows the other’s HIV status.  other’s HIV status. 

Do not have sex when Do not have sex when you are taking drugs you are taking drugs or drinking alcohol or drinking alcohol because being high because being high can make you more can make you more likely to take risks. likely to take risks.

Get tested for HIV Get tested for HIV Talk about HIV and other Talk about HIV and other

STDs with each partner STDs with each partner before you have sex. before you have sex.

Learn as much as you Learn as much as you can about each partner’s can about each partner’s past behavior (sex and past behavior (sex and drug use), and consider drug use), and consider the risks to your health the risks to your health before you have sex. before you have sex.

Use a latex condom and Use a latex condom and lubricant every time you lubricant every time you have sex. have sex.

Do not inject illicit drugs Do not inject illicit drugs

Symptoms of HIV InfectionSymptoms of HIV Infection rapid weight loss rapid weight loss dry cough dry cough recurring fever or profuse recurring fever or profuse

night sweats night sweats profound and unexplained profound and unexplained

fatigue fatigue swollen lymph glands in the swollen lymph glands in the

armpits, groin, or neck armpits, groin, or neck diarrhea that lasts for more diarrhea that lasts for more

than a week than a week white spots or unusual white spots or unusual

blemishes on the tongue, in blemishes on the tongue, in the mouth, or in the throat the mouth, or in the throat

pneumonia pneumonia red, brown, pink, or purplish red, brown, pink, or purplish

blotches on or under the skin blotches on or under the skin or inside the mouth, nose, or or inside the mouth, nose, or eyelids eyelids

memory loss, depression, and memory loss, depression, and other neurological disorders other neurological disorders

You cannot rely You cannot rely on symptoms on symptoms alone because alone because many people who many people who are infected with are infected with HIV do not have HIV do not have symptoms for symptoms for many years. many years.

http://http://www.hivtest.org/www.hivtest.org/

How HIV affects the How HIV affects the immune system immune system

HIV/AIDS TreatmentHIV/AIDS Treatment Reverse transcriptase (RT) inhibitors interfere

with the critical step during the HIV life cycle known as reverse transcription. During this step, RT, an HIV enzyme, converts HIV RNA to HIV DNA. There are two main types of RT inhibitors.

Protease inhibitors interfere with the protease enzyme that HIV uses to produce infectious viral particles.

Entry and fusion inhibitors interfere with the virus' ability to fuse with the cellular membrane, thereby blocking entry into the host cell.

Integrase inhibitors block integrase, the enzyme HIV uses to integrate genetic material of the virus into its target host cell.

Multidrug combination products combine drugs from more than one class into a single product.

Types of disease Types of disease transmissiontransmission

DiseaseDisease PathogenPathogen Type of AgentType of Agent Spread bySpread by

Influenza (flu)Influenza (flu) OrthomyxovirOrthomyxovirusus

VirusVirus Casual contactCasual contact

Chicken poxChicken pox Varicella-Varicella-zosterzoster

VirusVirus Casual contactCasual contact

German measlesGerman measles Rubella virusRubella virus VirusVirus Casual contactCasual contact

AIDSAIDS Human Human immunodeficiimmunodeficiency virusency virus

VirusVirus Non-casual Non-casual contactcontact

Lyme diseaseLyme disease Borrelia Borrelia burgdorferiburgdorferi

BacteriumBacterium Insect biteInsect bite

MeaslesMeasles Morbilli virusMorbilli virus VirusVirus Casual contactCasual contact

MononucleosisMononucleosis Epstein-Barr Epstein-Barr virusvirus

VirusVirus Casual contactCasual contact

SyphilisSyphilis Treponema Treponema pallidumpallidum

BacteriumBacterium Sexual actsSexual acts

MalariaMalaria PlasmodiumPlasmodium ProtozoaProtozoa Insect biteInsect bite