immunology final

immunology final - Chris Phelps Immunology Final April 27,...

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Chris Phelps Immunology Final April 27, 2007 1.) Cytotoxic T-cells are only activated by antigen presenting cells which present the endogenous antigen via MHC class I. The cell which acts as the antigen presenting cell has become infected by a virus. The virus replicates and peptide fragments are bound by MHC class I molecules in the endoplasmic reticulum of the infected cell. This interaction, coupled with the binding of a CD8 molecule from the surface of the CD8 T-cell, activates the T-cell into killing the infected cell. The above response is to a normally functioning virus particle which has infected a particular cell. In the case of vaccines which use an inactivated form of the virus, the viruses are unable to infect cells. On the surface of B-cells however is a substance known as antibody. Antibody can recognize and bind antigen of a specific type. The B-cells with correctly rearranged gene sequences, upon binding to antigen proliferate and differentiate into plasma cells which mass produce the antibody for both destruction of the present antigen and also for long term memory of that specific antigen. In the instance of this type of vaccine, B-cells produce a response, but cytotoxic T-cells do not. 2.) The four different molecules of the immune system which bind intact or processed antigen are antibody, major histocompatibilty complex I & II, and the T-cell receptor complex. The T-cell complex is divided into two different types, an alpha-beta receptor and a gamma-delta receptor. It has a similar structure to that of the Fab region of the antibody. The T-cell receptor is
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anchored through the transmembrane region into the cytoplasm with a cytoplasmic tail. Just outside the membrane are two constant regions joined by sulfide bonds. At the tip is a variable region encoded for by the corresponding gene (alpha-beta or gamma-delta). The gene which encodes for this receptor undergoes a nearly identical process to the antibody gene rearrangement.
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immunology final - Chris Phelps Immunology Final April 27,...

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