Role of single amino acids in the recognition of a T cell epitope.

摘要: T cell epitopes can be defined by the use of synthetic peptides, which when added to APC efficiently mimic naturally processed Ag. Free peptide is thought bind cell-surface MHC glycoproteins and TCR then recognizes resulting complex. The specificity a tetanus toxin-specific human Th clone was investigated using complete replacement set peptides in every amino acid within minimal epitope replaced each 19 alternative genetically coded acids. Within epitope, found YSYFPSVI (tetanus toxin 593-600), small number substitutions could made without significant loss activity, as giving whose activity fell +/- 3 SD mean parent response. Y593 substituted with F, W, M, L, V, I; S594 G T; Y595, F596, P597 no other acids; S598 A; V599 S, I600 L. Rank ordering allowed precise description and/or interaction side chain epitope. Simplified theoretic calculations based on this study indicate that class II recognition has greater than 1 10(8). Competition experiments P597, are critical for binding its restricting element, HLA DR4Dw14.