Chapter_3 - Chapter 3 T-cells don't secrete antibodies....

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Chapter 3 T-cells don’t secrete antibodies. They have membrane-bound T-cell receptors (TCR). The receptors recognize peptide fragments of antigens that are bound to specialized antigen presenting glycoproteins called MHC molecules, which are on almost all cells of the body. **There are large number of variants of MHC molecules across the human population, which is the underlying determinant of tissue incompatibility in transplantation.** The TCR looks like the Fab arm of an IG. They have a V region that binds antigen and a constant region. T cells go through a similar gene rearrangement during development as B cells, but after antigen stimulation, there is no further mutation in the antigen binding site and there is not isotype switching. A TCR is made up of 2 polypeptide chains called the alpha chain and beta chain. After successful gene rearrangement, each T cell expresses one functional alpha and beta chain. The antigen binding site for both chains (alpha and beta) each have 3 loops, called CDR loops (CDR1, CDR2, CDR3). These form the hypervariable region (tip of V region). T cells only possess one antigen binding site (IGs=2). TCRs only recognize antigen, not for the generation of effector functioins The TCR alpha chain has a V, J, and one C gene segment. The beta chain has a V, D, and J gene segment and 2 C gene segments (only one C gene segment is used). SCID – sever combined immunodeficiency disease (RAG genes don’t work and no B and T cells.) T cells bearing gamma:delta TCRs make up less than 5% of all T cells. Antigen processing and presentation T cells can only recognize antigen in the form of a peptide bound to a MHC molecule on the surface of a human cell. There are two types of T cells; CD4 helper T cells and CD8 cytotoxic T cells. CD8 T cells kill cells that have been virally infected or infected by some other intracellular pathogen. CD4s helps other cells of the immune system to
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This note was uploaded on 04/07/2008 for the course PHS 3505 taught by Professor Carroll during the Spring '08 term at St. Johns Duplicate.

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Chapter_3 - Chapter 3 T-cells don't secrete antibodies....

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