RE: Ray29 Jun 2018 19:16
Yes random generation of codes, the thymus then deletes codes considered self, but the naive t cell can still activate against non specific antigens that are near ...
Recent advances have revealed some answers to these questions. For example, early experiments suggested that the selecting peptide might need to be related in sequence to the subsequently activating peptide for a particular T cell (4, 14, 33). Later experiments contradicted this idea, however. In particularPawlowski et al. 1996 showed that thymocytes bearing a transgenic TCR could be positively selected by peptides that were unrelated to the peptide that could activate T cells bearing the same TCR. Other experiments have shown that a single MHC/peptide combination selects an unexpectedly large number of T cells, suggesting that the specificity during positive selection of TCRs for peptide might not be especially tight (16, 23, 25).
In this report we describe experiments that address the latter question with the use of mice that express a single class II MHC protein bound to a single peptide. T cells selected on this combination were tested for their ability to respond to various peptide antigens, some of which were relatively unrelated in their TCR contact residues to the selecting peptide. T cells selected on the MHC/single peptide combination responded to all peptides tested. The sequences of the TCRs on these selected cells were related to but not identical to those of T cells from normal mice, specific for the same MHC/peptide combination. We conclude that the reaction between TCRs and MHC/peptide during positive selection does not necessarily dictate the peptide specificity of the selected, mature T cell. Moreover, MHC bound to a single peptide can select T cells specific for many different peptide ligands.
https://www.sciencedirect.com/science/article/pii/...
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