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Specific Defenses

Specific Defenses. The Immune System. Definitions. Innate (nonspecific) Defenses against any pathogen Immunity Specific antibody and lymphocyte response to an antigen Antigen (Ag) A substances that causes the body to produce specific

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Specific Defenses

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  1. Specific Defenses The Immune System

  2. Definitions • Innate (nonspecific) Defenses against any pathogen • Immunity Specific antibody and lymphocyte response to an antigen • Antigen (Ag) A substances that causes the body to produce specific antibodies or sensitized T cells • Antibody (Ab) Proteins made in response to an antigen

  3. Terminology • Serology Study of reactions between antibodies and antigens • Antiserum Generic term for serum because it contains Ab • Globulins Serum proteins • Gamma () globulin Serum fraction containing Ab

  4. Serum Proteins Figure 17.2

  5. Immunity Types • Acquired immunity Developed during an individual's lifetime • Humoral immunity Involves Ab produced by B cells • Cell-mediated immunity Involves T cells

  6. Acquired Immunity • Naturally acquired active immunity • Resulting from infection • Naturally acquired passive immunity • Transplacental or via colostrum • Artificially acquired active immunity • Injection of Ag (vaccination) • Artificially acquired passive immunity • Injection of Ab

  7. Antigenic Determinants • Antibodies recognize and react with antigenic determinants or epitopes. Figure 17.3

  8. Haptens Figure 17.4

  9. Antibody Structure Figure 17.5a-c

  10. IgG antibodies • Monomer • 80% of serum antibodies • Fix complement • In blood, lymph, intestine • Cross placenta • Enhance phagocytosis; neutralize toxins & viruses; protects fetus & newborn • Half-life = 23 days

  11. IgM antibodies • Pentamer • 5-10% of serum antibodies • Fix complement • In blood, lymph, on B cells • Agglutinates microbes; first Ab produced in response to infection • Half-life = 5 days

  12. IgE antibodies • Monomer • 0.002% of serum antibodies • On mast cells and basophils, in blood • Allergic reactions; lysis of parasitic worms • Half-life = 2 days

  13. Clonal Selection Figure 17.8

  14. Clonal Selection • Bone marrow gives rise to B cells. • Mature B cells migrate to lymphoid organs. • A mature B cells recognizes epitopes.

  15. Self-tolerance • Body doesn't make Ab against self • Clonal deletion • The process of destroying B and T cells that react to self antigens

  16. The Results of Ag-Ab Binding Figure 17.9

  17. Antibody titer: • Is the amount of Ab in serum Figure 17.10

  18. Monoclonal Antibodies • Hybridomas are produced by fusing a cancer cell with an Ab-secreting plasma cells • The hybridoma cell culture is immortal and produces monoclonal Abs (Mabs) • Immunotoxins: Mabs conjugated with a toxin to target cancer cells • Chimeric Mabs: Genetically modified mice that produce Ab with a human constant region • Humanized Mabs: Mabs that are mostly human, except for mouse antigen-binding

  19. Monoclonal Antibodies Figure 17.11

  20. Immune system cells communicate via cytokines • Interleukin-1 Stimulates TH cells • Interleukin-2 Activates TH, B, TC, and NK cells • Interleukin-12 Differentiation of CD4 cells • -Interferon Increase activity of macrophages • Chemokines Cause leukocytes to move to an infection

  21. Cell-Mediated Immunity • Specialized lymphocytes, mostly T cells, respond to intracellular Ags • After differentiating in the thymus, T cells migrate to lymphoid tissue • T cells differentiate into effector T cells when stimulated by an Ag • Some effector T cells become memory cells

  22. Pathogens entering the gastrointestinal or respiratory tracts pass through: • M (microfold) cells in • Peyer's patches which contains • Dendritic cells which are antigen-presenting cells and • T cells

  23. Dendritic cells present antigens Figure 17.12

  24. T Cells • Helper T Cells (CD4, TH) • TH1 Activate cells related to cell-mediated immunity • TH2 Activate B cells to produce eosinophils, IgM, and IgE • Cytotoxic T Cells (CD8, TC) • Destroy target cells with perforin

  25. Helper T Cells Figure 17.13

  26. Cell-mediated Cytotoxicity Figure 17.14

  27. Nonspecific Cells • Activated macrophages: Macrophages stimulated by ingesting Ag or by cytokines • Natural killer cells: Lymphocytes that destroy virus-infected cells, tumor Figure 17.15

  28. T-independent Antigens Figure 17.16

  29. Antibody-Dependent Cell-Mediated Cytotoxicity Figure 17.18

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