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Definition: Specific lymphocyte response to foreign antigens, including the development of immunological memory:
Definition: The process by which lymphocytes are activated and expanded (proliferated) by encounters with antigens that are specifically recognized by the receptor:
What type of lymphocyte 'directs' the adaptive immune response against specific antigens?
Helper T cells (CD4+ T cells)
What type of lymphocyte is the primary producer of antibodies in an adaptive immune response?
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.
Can a naive T cell be activated by a free-floating antigen?
No- only a professional phagocyte can activate a nTc.
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.
What cytokine is the end product of the ZAP-70 cascade which results in T cell proliferation?
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.
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.
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.
Definition: A substance that stimulates proliferation:
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.
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.
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.
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)
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.
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.
Th1 (helper T cell type 1) cells activate mainly what kind of immune cell?
Macrophages, primarily via IFN-gamma.
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.
IL-12 induces Naive CD4+ T cells to differentiate into what kind of Th cell?
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)
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.
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.
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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