Exam2 - Starsha McGrath January 10, 2008 MIC519 Immunology...

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January 10, 2008 MIC519 – Immunology Decker Exam 2 – Redo 1. Toll-like receptors (TLRs) play a key role in the activation of the innate immune system. The TLRs that are able to recognize many of the different types of pathogens and host- derived proteins are the TLRs that are expressed mainly on macrophages and dendritic cells. Macrophages phagocytose debris and pathogens that enter the cell. “Dendritic cells are the most potent antigen-presenting cells, inducing both naïve and memory immune responses.” Macrophages and DCs are primarily involved in the innate immune response, but they are also essential in the adaptive immune response as antigen- presenting cells (APCs). Therefore, TLR signaling promotes activation of an innate immune response and then triggers antigen-specific adaptive immunity (Medzhitov et al., 1997, Kaisho et al., 2002, Akira et al., 2001, Aderm et al., 2001). TLR signaling acts to trigger the adaptive immune response by enhancing the expression of MHC molecules and inducing tumor antigen-specific cytotoxic T lymphocytes (CTLs) which are important for eliminating tumor cells. TLR signaling also increases the production of IL- 12 which is a major helper-T cell 1 (Th1)-inducing cytokine, on APCs (Kaisho et al., 2002, Akira et al., 2001, Akira et al., 2001, Melief et al., 2002). IL-12 is one of the first cytokines produced by macrophages during infection. The DCs matured by TLR stimulation may induce T-cell differentiation toward a Th1 response by presenting antigens to the T cells while promoting a Th1-leading situation in that environment. T cell immunity to intracellular bacteria is triggered by phagocytic cells for both MHC class I and II-restricted Ag presentation functions. These APC stimulate CD4+ T cells specific for bacterial Ags which in turn feed back through the release of cytokines such as IFN- to phagocytic cells harboring replicative intracellular bacteria by increasing their bacteriostatic and bactericidal functions. Macrophages represent an APC partner for T cells. Efficient uptake of bacteria by macrophages is mediated by various surface molecules such as FcR. Activated macrophages are a source of IL-12 which plays a pivotal role in host resistance to bacterial infection by stimulating IFN- production by NK cells and by promoting Th1 responses. Dendritic cells represent the most potent APC for priming naive T cells, an important source of IL-12 following microbial stimuli, and consequently are highly efficient in inducing antiviral and antitumor immune responses. (Jiao et al., 2002). 2. From the table, the T cells function is to detect memory effector T cells. If the tyrosinase-specific T cells expressed high levels of CD45RA and not CD45RO, and low levels of CD44, then the T cells that they were detecting would have been naive T cells. MHC/peptide tetramers can be used to stain T cells in an antigen-specific manner to
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This note was uploaded on 04/02/2008 for the course MIC 519 taught by Professor Decker during the Fall '07 term at University of Arizona- Tucson.

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Exam2 - Starsha McGrath January 10, 2008 MIC519 Immunology...

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