ANALYSIS OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS I-RESTRICTED HAPTEN RECOGNITION BY MUTATION OF THE V-J JOINING OF T-CELL RECEPTOR-ALPHA CHAINS

Hapten-specific T cell responses are responsible for chemically induce d immune disorders. However, the molecular details of hapten interacti ons with T cell receptors (TCR) are poorly understood. Recent studies of trinitrophenyl (TNP)=specific responses revealed major histocompati bility complex-associated TNP-peptides as dominant epitopes For CD8(+) and CD4(-) T cells. The present study is based on the observation tha t two H-2K(h)/TNP-spccific CTL clones (II/7 and III/1), differing excl usively in two amino acids of their TCR alpha chains, also differed in their carrier specificities for various TNP-peptides. The genes of th e two alpha chains and the common beta chain were cloned into expressi on vectors. Transfection of the TCR alpha chain of clone III/1 into a hybridoma of clone II/7 also transferred the fine specificity of clone III/1, indicating that the small cc chain v ariations were indeed res ponsible for the different carrier specificities. Point mutations brid ging the difference between the alpha chains of clones II/7 and III/1 and functional studies of the respective TCR alpha beta transfectants into a TCR-negative hybridoma revealed an unexpected result: the two r eceptors did not represent examples of structural complementarity for different sets of hapten-peptide conjugates: rather, they resembled tw o structures of principally similar spt cificity but of significantly different overall affinity. This was demonstrated more directly by com paring the fine specificities of III/1 transfectants expre ssing or no t expressing the co-receptor CD8: the CD8-negative III/1 transfectant assumed a specificity pattern indistinguishable from that of a CD8-exp ressing. II/7-derived transfectant. Hence, comparable alterations of a ntigen recognition may be induced either by subtle TCR alterations or by removal of CD8. i.e. by the presence or absence of a non-polymorphi c adhesion molecule.