SPECIFIC T-CELL RECOGNITION OF KINETIC ISOMERS IN THE BINDING OF PEPTIDE TO CLASS-II MAJOR HISTOCOMPATIBILITY COMPLEX

Helper T cells are triggered by molecular complexes of antigenic pepti des and class Il proteins of the major histocompatibility complex. The formation of stable complexes between class II major histocompatibili ty complex proteins and antigenic peptides is often accompanied by the formation of a short-lived complex, In this report, we describe T cel l recognition of two distinct: complexes, one short-lived and the othe r long-lived, formed during the binding of an altered myelin basic pro tein peptide to I-A(k). One myelin basic protein-specific T cell clone is triggered by only the short-lived complex, and another is triggere d by only the stable complex, Thus, a single peptide bound to a partic ular class II molecule can activate different T cells depending on the conditions of the binding reaction.