The role of peptide in the positive selection of CD8+ T cells in the thymus.

Recent experiments using fetal thymus organ culture (FTOC) systems derived from class I deficient mice have provided evidence supporting the view that specific recognition of class I MHC plus peptide complexes is required for the positive selection of CD8+ T cells. The addition of class I binding peptides to FTOC systems derived from beta 2-microglobulin and TAP 1 deficient mice induced the positive selection of CD8+ T cells in a peptide specific manner. The specific recognition of peptide during positive selection implies that the repertoire of specificity's exhibited by CD8+ T cells is at least in part determined by the repertoire of self-peptides presented by class I MHC in the thymus.