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Chapter 39

Chapter 39. Immunity. Immunity. The ability to defend against infectious agents, foreign cells, and cancer cells. Immune System. Antigen —any molecule that the body recognizes as nonself and that provokes an immune response. Three lines of defense Protective barriers Innate immunity

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Chapter 39

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  1. Chapter 39 Immunity

  2. Immunity • The ability to defend against infectious agents, foreign cells, and cancer cells

  3. Immune System • Antigen—any molecule that the body recognizes as nonself and that provokes an immune response. • Three lines of defense • Protective barriers • Innate immunity • Adaptive immunity

  4. Protective Barriers • Intact skin—prevents entry • Ciliated mucous membranes—trap & sweep out foreign particles • Oil & other exocrine glands—secrete bacterial inhibitors • Low pH in digestive & urinary tract—kill invading bacteria • Normal microbes of skin, GI tract, genitals—keep foreign bacteria in check

  5. Non-Specific Defenses • Complement • 20-30 proteins • Coat invading pathogens • Some form pores that cause pathogen to lyse • Some promote inflammation • Some attract phagocytic cells

  6. Non-Specific Defenses • Macrophages • Non-specific & specific • Ingest dust and debris (especially in lungs) • Ingest microbes

  7. Non-Specific Defenses • Inflammatory Response • Invader penetrates • Injured cells produce chemicals • Cytokines & histamines • Capillaries dilate • WBCs penetrate more easily • Opsonization—invader coated in complement • Chemotaxis—WBCs attracted to site due to alarm chemicals • WBCs form macrophages • Macrophages ingest & digest

  8. Non-Specific Defenses • Inflammatory Response (cont.) • Redness & warmth—blood rushing to site • Swelling—tissue fluids increasing, large numbers of macrophages • Pain—increased fluid pressing on nociceptors

  9. Non-Specific Defenses • Fever • Macrophages release signals to hypothalamus • Mild fever increases enzyme activity & metabolism • Formation & action of phagocytes increases • Tissue repair increases • Many microbes grow slowly at higher temperatures

  10. Specific Defenses • Relies on detecting antigens • B & T lymphocytes • One of types of WBCs • Central to adaptive immunity • Antibody-mediated immunity • Cell-mediated immunity

  11. Antibody-Mediated Immunity • Also called “humoral” immunity • B lymphocytes produced in bone marrow • Each B cell is antigen-specific • Antigen receptors on surface (determined gentically) • Will only respond to specific antigen

  12. Antibody-Mediated Immunity • B cell matches to antigen • Engulfs, digests antigen • Displays antigen fragments • Helper T cell attracted • T cell releases cytokines • B cell stimulated to multiply & change into plasma cells • Plasma cells produce antibodies

  13. Antibody-Mediated Immunity • Once infection is over, most B cells die • Some retained as memory B cells • On future infections, can respond faster

  14. Antibody-Mediated Immunity • Antibodies produced by plasma cells • Antibody Structure • Light chain • Heavy chain • Antigen binding site

  15. Antibody-Mediated Immunty • Antibody Types (Immunoglobulin) • IgG • Most numerous & diverse (75-85%) • Bacteria, viruses, toxins • Crosses placenta • IgM • First secreted • Stimulates complement cascade • IgD • Activates & matures B cells • IgA • Saliva, sweat, milk, etc. • Prevents pathogens from attaching to epithelium • IgE • Binds to basophils • Release histamines during inflammation & allergic reactions

  16. Antibody-Mediated Immunity • Antibody Functions (PLAN) • Precipitation • Form large complexes with molecules • Complexes settle in solution • Easier to phagocytize • Lysis • Enhances complement action of making holes in cells • Agglutination • Form large complexes with cells • Complexes clump • Easier to phagocytize • Neutralization • Block binding sites used to invade tissue cells

  17. Cell-Mediated Immunity • T lymphocytes • Produced in bone marrow • Mature in thymus gland • Cannot recognize antigens • Antigen-presenting cell (APC) • Macrophages, dendritic cells • Engulf antigen • Complex formed on cell surface • Binds to T cell, activating it

  18. Cell-Mediated Immunity • T cell encounters APC • T cell activated • T cell multiplies, specializes • Can attack pathogens directly • Can attack cells invaded by pathogens

  19. Cell-Mediated Immunity • Cytotoxic T cells • Kill infected cells by perforating cell membrane • Primary defense against infected cells, tumors • Cause rejection of tissue & organ transplants • Helper T cells • Stimulate B & T cell maturity • Enhance macrophage activity • Memory T cells • Like memory B cells, remain after infection • Suppressor T cells • Slow & stop immune response after infection over

  20. Types of Immunity • Natural • Active production—exposed to pathogen • Passive production—through placenta or milk • Artificial • Active production—vaccination with dead or altered pathogen • Passive production—direct injection of antibodies or anti-serum

  21. Immune Disorders • Immunodeficiency • Weak immune system • Usually due to low WBC count • Cancer, HIV, chemotherapy, radiation • Autoimmune disease • Body recognizes cell proteins as “non-self” antigens • Lupus, rheumatoid arthritis, multiple sclerosis • Hypersensitivity • Immune response unusually strong • Acute—minutes (anaphylaxis) • Subacute—minutes to hours (blood transfusion) • Delayed—hours to days (poison ivy)

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