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Chapter 43 ~ The Body’s Defenses Lines of Defense Nonspecific Defense Mechanisms…… Phagocytic and Natural Killer Cells • Neutrophils 60-70% WBCs; engulf and destroy microbes at infected tissue • Monocytes 5% WBCs; develop into…. • Macrophages • Eosinophils 1.5% WBCs; destroy large parasitic invaders (blood flukes) by enzymatic hydrolysis • Natural killer (NK) cells destroy virus-infected body cells & abnormal cells The Inflammatory Response • 1- Tissue injury; release of chemical signals – histamine (basophils/mast cells): causes Step 2... • 2/3- Dilation and increased permeability of capillary – chemokines: secreted by blood vessel endothelial cells mediates phagocytotic migration of WBCs • 4- Phagocytosis of pathogens – fever & pyrogens: leukocyte-released molecules increase body temp Specific Immunity • Lymphocyctes •pluripotent stem cells... • B Cells (bone marrow) • T Cells (thymus) • Antigen: a foreign molecule that elicits a response by lymphocytes (virus, bacteria, fungus, protozoa, parasitic worms) • Antibodies: antigen-binding immunoglobulin, produced by B cells • Antigen receptors: plasma membrane receptors on B and T cells Activating B or T cells • Effector cells: short-lived cells that combat the antigen • Memory cells: long-lived cells that bear receptors for the antigen • Clonal selection: antigen-driven cloning of lymphocytes Induction of Immune Responses • Primary immune response: lymphocyte proliferation and differentiation the 1st time the body is exposed to an antigen • Plasma cells: antibody-producing effector B-cells • Secondary immune response: immune response if the individual is exposed to the same antigen at some later time~ Immunological memory Self/Nonself Recognition • Major Histocompatability Complex (MHC): body cell surface antigens – self genes • Class I MHC: found on all nucleated cells • Class II MHC: found on macrophages, B cells, and activated T cells • Antigen presentation: – cell displays an intracellular protein to antigen receptor on a nearby T cell Helper T lymphocytes • Function in both humoral & cell-mediated immunity • Stimulated by antigen presenting cells (APCs) Antibody Structure • 2 heavy chains and 2 light chains joined by disulfide bridges • Antigen-binding site (variable region) • • • • Antibody Function Neutralization (opsonization): antibody binds to and blocks antigen activity Agglutination: antigen clumping Precipitation: cross-linking of soluble antigens Complement fixation: activation of 20 serum proteins, lyse viruses and pathogenic cells Immunity in Health & Disease • Acquired Immunity – Conferred immunity by recovering from disease – immunization and vaccination; produces a primary response • Passive immunity: transfer of immunity from one individual to another – natural: mother to fetus; breast milk – artificial: rabies antibodies • ABO blood groups (antigen presence) • Rh factor (blood cell antigen); Rh- mother vs. an Rh+ fetus (inherited from father) Abnormal immune function • • • Allergies (anaphylactic shock): hypersensitive responses to environmental antigens Autoimmune disease: multiple sclerosis, lupus, rheumatoid arthritis, insulindependent diabetes mellitus Immunodeficiency disease: SCIDS (bubble-boy); A.I.D.S. 1. What immune system activities occur in the 1st, 2nd, 3rd lines of defense (primary/secondary/specific responses)? 2. Describe how histamine works in the inflammatory response. 3. What are the roles of the different kinds of immune cells (B cells, helper T, cytotoxic T, macrophages, memory cells, etc)? 4. What is Rh factor and under what circumstances does it pose a risk during pregnancy? 5. What immune activities occur at each stage of an immune response following exposure to a pathogen? 6. How are the ABO blood groups important in immunity? (what happens if the wrong blood type is given?) 7. What genetic process enables antibodies to have variation in their specificity? 8. What is the function of MHC? 9. How does phagocytosis work? 10. How do pathogens evade the second lines of defense? 11. What are antigens? What types of substances can act as antigens? 12. What mechanisms do pathogens (such as Salmonella) use to evade the immune system and cause infection? 13. What general activities comprise the overall process of a specific immune response? 14. What do antibodies do to help fight infection by pathogens? 15. Distinguish between B and T cells. 16. Compare/contrast autoimmune disease with immune deficiency disease. 17. How are helper T cells activated? 18. What is clonal selection and what causes it? 19. What is the role of histamine in the inflammatory response?