PEPTIDE ANTAGONISM AND T-CELL RECEPTOR INTERACTIONS WITH PEPTIDE-MHC COMPLEXES

We describe antagonist peptides that specifically inhibit cytolytic ac tivity of T cell clones and lines that express the antigen-specific re ceptor of CD8(+) T lymphocyte clone 2C, which recognizes peptides in a ssociation with syngeneic (Kb) and allogeneic (Ld) MHC proteins. Addit ion of an antagonist peptide that can bind to K-b on 2C cells decrease d the tyrosine phosphorylation of CD3 zeta chains elicited by prior ex posure of the cells to an agonist peptide-K-b complex. Contrary to pre vious agonist-antagonist comparisons, the 2C T cell receptor had highe r affinity for an antagonist peptide-K-b complex than for a weak agoni st peptide-K-b complex. This difference is considered in light of evid ence that antigen-specific receptor affinity values can be substantial ly higher when determined with the receptor on live cells than with th e receptor in cell-free systems.