Micro I8-9

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  1. Definition: Specific lymphocyte response to foreign antigens, including the development of immunological memory:
    Adaptive immunity
  2. Definition: The process by which lymphocytes are activated and expanded (proliferated) by encounters with antigens that are specifically recognized by the receptor:
    Clonal Selection.
  3. What type of lymphocyte 'directs' the adaptive immune response against specific antigens?
    Helper T cells (CD4+ T cells)
  4. What type of lymphocyte is the primary producer of antibodies in an adaptive immune response?
    B cells.
  5. True/False: naive T cells require only TCR/CD3 signaling in order to activate (i.e.: it only requires the correct MHC class and peptide antigen to be presented).
    False: naive T cells also must have costimulation with B7/CD28 receptors.
  6. Can a naive T cell be activated by a free-floating antigen?
    No- only a professional phagocyte can activate a nTc.
  7. Phosphorylation of what signaling molecules follow the TCR recognition of and antigen/MCH complex?
    CD3 and ITAM (immunotyrosine activation motif). This begins the signal cascade which will activate a naive T cell.
  8. What cytokine is the end product of the ZAP-70 cascade which results in T cell proliferation?
  9. Cyclosporine A and FK-506 (tacrolimus) are two immunosuppressive drugs which function by what mechanism?
    The both inhibit production of IL-2, which prevents T cell proliferation.
  10. True/False: Out of the three nuclear transcription factors for IL-2 (NFAT, NF-kappaB, and AP-1), you only need 2 out of the three to be properly expressed in order to have functioning IL-2.
    False: you must have all three TFs to have functional IL-2.
  11. In ZAP-70 deficiency, what is the presence and functional status of Th cells and CTK cells, and why?
    • CTK cells (CD8+ T cells) are not present at all;
    • Th cells (CD4+ T cells) are present, but non-functional.
    • Th cells must produce IL-2 in order to proliferate and be functional (ZAP-70 is required for IL-2), and Th cells must be activated for CTK to be recruited.
  12. Definition: A substance that stimulates proliferation:
  13. True/False: Mitogenic lectins do not require APCs in order to activate T cells.
    True. This makes them useful for in vitro T cell activation functional assays.
  14. What are two mechanisms that the immune system uses to help a specific antigen connect with its specific naive T cell (odds of 1:100000)?
    • Naive T cells cycle between blood, tissues and lymph organs, increasing likelihood of contact
    • Dendritic cells, after phagocytosing antigen, migrate toward lymph nodes + spleen, further increasing likelihood of finding nTc.
  15. Following activation by specific antigens, naive T cells differentiate into what two kinds of T cells?
    Effector T cells (helper and CTK) or memory T cells.
  16. As opposed to naive T cells which bind to high endothelial cells in lymphatic vessels, effector T cells (Th and CTK) bind to what kinds of endothelium?
    Activated vascular endothelium at sites of infection (express VLA-4 receptor which binds to VCAM-1 in inflamed tissue)
  17. Why do T cells arrive at sites of inflammation several hours to days after the infection has started?
    Endothelial cells must generate and express VCAM-1 before effector T cells can leave the circulation and move into inflamed tissue. On the other hand, E-selectin is expressed almost immediately, allowing Neutrophils to exit the circulation within minutes-hours.
  18. Why are memory T cells activated more rapidly than naive T cells?
    Activation is independent of costimulation (rf CD28), so fewer 'pieces' need to fall in place to successfully activate the memory cell.
  19. Th1 (helper T cell type 1) cells activate mainly what kind of immune cell?
    Macrophages, primarily via IFN-gamma.
  20. Th2 (helper T cell type 2) cells activate mainly what kind of immune cell?
    B cells, using a number of cytokines including IL4, IL5 and IL15.
  21. IL-12 induces Naive CD4+ T cells to differentiate into what kind of Th cell?
  22. True/False: The cytokines produced by Th1 and Th2 cells potentiate each other's actions, thereby allowing the immune defense to work even faster.
    • False: the cytokines inhibit each other
    • (rf: Th1 release IFN-gamma, which inhibits Th2)
    • (rf: Th2 release TGF-beta and IL-10 which inhibit Th1)
  23. Match "Lepromatous leprosy" and "Tuberculoid leprosy" with immune cell types associate with them.
    Lepromatous is associated with Th2 responses, and Tuberculoid is associated with Th1 responses.
  24. True/False: Th cells are required for the activation of naive CD8+ T cells.
    • False: Naive CD8+ cells can be activated directly by dendritic cells without the presence of Th cells (pathway 1).
    • However Th cells can also help activate them, as in the case of pathways 2 and 3.
  25. If HIV targets CD4+ T cells, but not CD8+ T cells, why do patients with AIDS show a dramatic decrease in CD8+ T cell expression?
    2 out of the 3 mechanisms for activating CD8+ T cells require functional CD4+ T cells. While some CD8+ cells will be activated in AIDS patients, the number of cells will be dramatically decreased.
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Micro I8-9
Immunology lectures I8 and I9
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