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Adaptive Immunity

Adaptive Immunity. Adaptive immunity develops as the need arises. Two types: - Humoral immunity - Mediated by B cells (B lymphocytes) - Produce antibodies that directly target antigens of invaders - Cell-mediated immunity - Involve T cells (T lymphocytes)

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Adaptive Immunity

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  1. Adaptive Immunity • Adaptive immunity develops as the need arises. • Two types: • - Humoral immunity • - Mediated by B cells (B lymphocytes) • - Produce antibodies that directly target antigens of invaders • - Cell-mediated immunity • - Involve T cells (T lymphocytes) • - Control antibody production and can directly kill infected host cells

  2. The immune system does not recognize the whole microbe, but innumerable tiny pieces of it. - Each small segment of an antigen that elicits an immune response is called an epitope or an antigenic determinant. Figure 24.2

  3. Antibody Structure and Diversity An antibody (immunoglobulin) is a Y-shaped structure made up of four polypeptides: - Two large heavy chains and two smaller light chains, connected by disulfide bonds Figure 24.7

  4. An antibody has constant and variable regions. - Variable regions form the antigen-binding site. Functional parts of the antibody can be separated following certain protease treatments. Figure 24.9

  5. All antibody isotypes have the same basic structure. - However, each has a unique “super” structure. Figure 24.11

  6. Time Course of an Immune Response

  7. Primary vs. Secondary Antibody Responses Figure 24.13

  8. Levels of the Immune Response

  9. Levels of the Immune Response

  10. Adaptive Responses Are Specific to Individual Molecules • Antigen: the molecule recognized by the response • Each cell can only recognize one antigen

  11. B cells differentiate by clonal selection. - When a B cell contacts its cognate antigen, it is stimulated to proliferate and differentiate into plasma cells (secrete antibodies) and memory cells. Figure 24.14

  12. Basic Steps in Antibody Formation Figure 24.17

  13. The Major Histocompatibility Complex Consists of membrane proteins with variable regions that can bind antigens: - Class I MHC: Found on all nucleated cells - Class II MHC: Found only on antigen-presenting cells Figure 24.20

  14. Figure 24.21

  15. T Cell Receptors • TCRs associatd with CD3 proteins on cell surface • - Bind antigens only if attached to MHC • - Complex transduces signal into cell, triggering T-cell proliferation. Figure 24.22

  16. Animation: The Activation of the Humoral and Cell-Mediated Pathways Cell-Mediated Immune Response Click box to launch animation

  17. Figure 24.24

  18. Figure 24.28

  19. Figure 24.30

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