Briefly describe positive and negative selection of T cells in the thymus
What will be an ideal response
T cells respond to antigen that is presented to them in conjunction with MHC antigens. Pre–T cells possess both the
CD4 and the CD8 markers. First, a positive selection process is done in which only cells that can bind to MHC
survive. Cells that cannot bind to MHC cannot react to antigen, so they are killed. Second, a negative selection
process is done to prevent reaction against self-antigens. Any remaining T cells that bind strongly to MHC antigens
are killed as they might react against self-tissues. What remains are T cells that bind weakly to MHC antigens, but if
a second antigen is presented with the MHC, then the bond becomes stronger and the T cell is activated. T cells that
bind to MHC Class I molecules retain the CD8 receptor, and T cells that bind to MHC Class II molecules retain the
CD4 receptor.
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Write the correct meaning for HDS:
What will be an ideal response?