Immune system

Chapter 43

Pathogen:Infectious agentInnate immunity:NonspecificAcquired immunity:Specific Previous exposure

Acquired Immunity

ActiveDiseaseVaccineTransfer of lymphocytes from a donor (bone marrow transplant)PassiveMaternal antibodiesImmunoglobulins (gamma globulins)

Defense

First line– Skin

Second line– Cell counterattack

Third line – Immune response (antibodies)– Specific

First-line

Skin1. Impenetrable barrier2. Oil & sweat glandsSkin pH--3-5 3. Sweat contains lysozymeEnzyme digests bacterial walls4. Prevents water loss

Skin

First line

Lysozyme in salivaStomach acid Digestive enzymes in gutAirway mucousCilia in airways Acidic urine

First line

Trachea

Second line

InvadersLymphatic systemDefense cells Adenoids, tonsils Thymus, spleenLymph nodes, lymph capillaries & ducts

Lymphatic system

Second line

WBCAntimicrobial proteinsInflammatory response

Second line

Leukocytes (WBC)Circulating in body1. Macrophages (monocytes)Kill invaders by ingesting them PhagocytosisIngestion

Fig. 43-3

Microbes

PHAGOCYTIC CELL

Vacuole

Lysosomecontaining enzymes

Second line

2. NeutrophilsMost abundant WBC PhagocytosisRelease chemicals--kill bacteriaAlso kills other neutrophils

Second line

3. EosinophilsWBCLow phagocytic activityParasite defense

Second line

Antimicrobial proteins1. Complement systemProteins found in plasmaAttack bacterial or fungal cell wallsCause cells lysisSignals other defense responses

Second line

2.InterferonsParacrine polypeptideProtect cells in area of virusPrevent viral replicationCancer defense

Second line

3. Natural killer cellsKills cells infected by a virusHelp fight cancer cells

Second line

Inflammatory responseLocal, non-specificHistamines & prostaglandinsVasodilationIncreased blood flow to area Edema or swellingWBC (phagocytic), pus formationShock, systemic

Second line

Second line

Inflammatory responseElevated temperature (fever)Interleukin-1 Released by MacrophagesDirects hypothalamus to increase tempHelps stimulate defense response

Third line

Specific responseLymphocytesT-cells---cellular responseB-cell---humoral responseAntibodies

Third line

Antigen Foreign moleculeEpitopeAntigen determinantLocated on surfaceCauses a specific immune response

Third line

Self-versus-nonself recognitionGenes code for specific proteins Major Histocompatibility Complex proteinsMHC proteinsCell recognitionGlycoproteins on surface of cells

Third line

B-cell lymphocytesMade & develops in bone marrowBecomes a plasma cellProduce antibodies in response to specific antigensImmunoglobulins (Ig)AntibodiesHumoral immunity

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Third line

B-lymphocyte structureAntigen receptorSpecificPlasma membrane

Third line

Light chains2 short polypeptidesHeavy chains2 identical long polypeptides 4 chains held together by disulfide bondForms Y-shaped molecules

Fig. 43-9a

Antigen-bindingsite

Antigen-binding site

Disulfidebridge

Variableregions

Constantregions

Transmembraneregion

Plasmamembrane

Lightchain

Heavy chains

Cytoplasm of B cell

(a) B cell receptor

B cell

V

V

C C

V

V

C C

Fig. 43-10

Antigen-binding sites

Antigen-bindingsites

Epitopes(antigenicdeterminants)

Antigen

Antibody B

Antibody CAntibody A

CC

CV

V

V

V

C

Antibodies

Plasma cells release antigen receptorSpecific for antigensArms of the Y shaped moleculeHave different aa sequences

Antibodies

IgM first responseAggregation of complement proteinsIgG major form, second responseStimulates phagocytosis by macrophagesIgD receptors for antigens on B cellsIgAPresent in breast milk, mucous, salivaProvide protection to newborns

Antibodies

IgERelease histaminesBind to mast cellsInsert heavy chain into mast cellsInitiate inflammatory responsePresence of antigensVasodilation

Antibodies

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Third line

T-cell lymphocytesMade in bone marrowProcessed in thymus glandRegulate immune responsesAttack cells with specific antigensCell-mediated immunity

Fig. 43-9b

Antigen-bindingsite

Variableregions

Constantregions

Transmembraneregion

Plasmamembrane

T cell

chain chain

Disulfide bridge

Cytoplasm of T cell

(b) T cell receptor

C C

VV

Third line

T-cells1. Helper T cells (CD4)Initiate response based on antigens2. Memory T cellsRemember previous antigens

Third line

3. Cytotoxic T cell (CD8)Lyse cells infected by virus4. Suppressor T cellsTurn off immune response

Third line response

AntigenMacrophage process antigenSecrete cytokines (interleukins or interferons)Stimulates T helper cells

Third line response

Recognize antigensAntigen receptor on T-cells Bind to antigensTriggers T-cytotoxic cells, T-memory cellsCytotoxic cells destroy infected cellsStimulates B cells

Third line response

Antigen receptor on B-cellBinds foreign antigenTriggers formation of a clone of plasma cellsClones produce antibodiesAntibodies bind invading antigen Prevent affects of antigenDestruction or blocks effect

Immune response Macrophage

⇓ Helper T-cell

⇙ ⇘ B-cell Cytotoxic T-cell ⇙ ⇘ ⇙ ⇘Plasma Memory Memory Cytotoxic cells cells cells T-cells ⇓Antibodies

T-cells

Cytotoxic T-cellsAttack transplants (skin grafts) Considered foreign tissueDestroy cancer cellsInterferon (lymphomas, renal Ca, melanoma, Kaposi’s sarcoma and Breast Ca)Interleukin (tx cancer)

B-cells

Primary immune responseFirst exposureLasts about 2 weeksMemory cells are also produced during the first exposureSecondary immune responseActivates memory cellsResponse faster & lasts longer

Immune System Summary

First lineSkin, cilia, enzymes, pH of skinSecond lineWBC (macrophages, neutrophils, natural killer cells, eosinophils)Antimicrobial proteinsInflammatory response

Immune System Summary

Third lineLymphocytes (B & T)Antibodies (immunoglobulins)IgM, IgG, IgA, IgE, IgD

Monoclonal antibodies

Antibodies specific for one antigenCell cultures produce large quantitiesUse in lab testsPregnancy testsAntibody to HCG (human chorionic gonadotropin)

HIV

Human immunodeficiency virusAttacks + destroys CD4+ T-cellsT-cells secrete a suppressing factor Blocks other T-cellsInfects macrophages & brain cells

Autoimmune diseases

Systemic LupusRheumatoid arthritisHashimoto thyroiditis

Allergy

Allergens (antigens)Release IgEBinds mast cells & basophilsStimulates release of chemicals HistamineDrop in BP

Allergy

Anaphylactic shockWidespread histamine responseDeathBee stings or peanuts or penicillinContact dermatitis Delayed responsePoison ivy, poison oak

Blood types (ABO)

Blood type

Surfaceantigens

Antibodies

A A anti B

B B

anti A

AB AB none

O none anti A & B

ABO

Rh factor