A monoclonal antibody (OT145) specific for the T cell antigen receptor V beta 6.7a allele detects an epitope related to a proposed superantigen-binding site.

A mAb, OT145, recognizes a TCR allotype encoded by one of two alleles of the V beta 6.7 gene. The peptide products of the two V beta 6.7 alleles differ because of nonconservative amino acid substitutions at positions 38 and 72. V beta 6.7a encodes ser38 and gly72, whereas V beta 6.7b encodes arg38 and glu72. We show here that the binding of mAb OT145 ot the beta-chain of TCR is lost when residue 72 of V beta 6.7a is mutated from gly to glu. The binding of OT145 is not affected by mutation of residue 38 from ser to arg. Thus, OT145 recognizes an epitope related to position 72. Residue 72 of the beta-chain of the TCR is located at a putative superantigen-binding site.