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Adaptive immunity Specificity Memory Distinguishes self from non-self

Adaptive immunity Specificity Memory Distinguishes self from non-self Components of adaptive immunity: Humoral Cell-mediated Principles of vaccination Immune deficiency and its consequences. Adaptive immunity takes several days to develop (to first exposure to antigen)

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Adaptive immunity Specificity Memory Distinguishes self from non-self

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  1. Adaptive immunity Specificity Memory Distinguishes self from non-self Components of adaptive immunity: Humoral Cell-mediated Principles of vaccination Immune deficiency and its consequences

  2. Adaptive immunity takes several days to develop (to first exposure to antigen) Cells proliferate Antibodies are produced Cytokines (signaling molecules) are produced Meanwhile, innate mechanisms act Adaptive mechanisms respond if infection has not been eliminated

  3. What are the adaptive mechanisms? Humoral immunity against “extracellular” antigens (bacteria, free viruses, toxins, etc.) antibodies and other molecules Cell-mediated against “intracellular” antigens (virus-infected cells; tumor cells) Responses are orchestrated by helper T cells

  4. p. 395

  5. How does humoral immunity work? B cells proliferate (in lymphatic tissues) and make antibodies Antibodies circulate and bind to antigen Neutralization; immobilization Immune complexes Facilitates phagocytosis Facilitates complement-mediated lysis B cells are activated clonally

  6. p. 401

  7. Clonal selection theory In bone marrow In the system Applies to T cells, too (p. 403)

  8. Antibodies have certain features in common but different classes (isotypes) have different properties. p. 398

  9. Variable region is unique, because each binds to a different antigen Constant regions fall into five classes (table 16.1, p. 399)

  10. What happens in the primary response that leads to antibody production? T cells respond to antigen; produce cytokines These cause B cells to proliferate and become plasma cells (antibody-producing cells) They become more able to react with antigen Class-switching (for appropriate response) Memory cells- more of them; they respond faster in subsequent responses

  11. p. 405

  12. T cells are not always involved in B cell response B cells can respond independently to polysac- charides (capsules); LPS Response is not as strong, especially in young children

  13. T cells also have an antigen-specific receptor Receptor is NOT released T cell must come in direct contact with antigen- presenting cell macrophage dendritic cell B cell How do these cells present antigen?

  14. What are the different types of T cells CD4(helper) and CD8 (cytotoxic) Both have antigen-specific receptors CD4 and CD8 molecules help with antigen presentation CD4 cells “see” antigen + MHC Class II CD8 cells “see” antigen + MHC Class I

  15. What is MHC? (major histocompatibility complex) Groups of cell- surface proteins, inherited When cells process antigen they return fragments (peptides) to the surface, bound to either MHC Class I or Class II MHC Class I is found on most cells MHC Class II on antigen-presenting cells (and levels can vary)

  16. Antigen-presenting cells process “exogenous antigen (bacterial, viral products), and activate responses against them Th1 cells- generally cell-mediated immunity Th2- generally humoral immunity

  17. MHC Class I displays “endogenous antigen” (like viruses) Many types of cells can present antigen with MHC Class I Often dendritic cells do this

  18. When T cells are activated they proliferate and produce cytokines Dozens of cytokines have been identified (and other cells can produce them, too) Cytokines bind to neighboring cells and activate them Recall that immune response is characterized by rapid proliferation and activation of cells!

  19. What do T cells actually do? T helper cells- cytokine production (Some are engaged in “delayed-type hypersen- sitivity) Cytotoxic T cells- cause apoptosis in targets What about natural killer cells? similar targets as CTLs no antigen-specific receptor no memory response have antibody receptors probably immune surveillance

  20. How DO immune cells avoid reacting with self antigens? Remember that T cells regulate the immune response Most self-reactive cells are eliminated in the thymus Antigen-presenting cells seem to be key

  21. Summary, p. 412

  22. Immune system responds to antigens that enter body in course of infection Vaccination: antigens are DELIBERATELY introduced to body to generate a specific immune response (and memory) Immune system normally distinguishes “harmful” antigens from self antigens or harmless substances What happens if it does not? What happens if immune system is deficient?

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