MAJOR CONTRIBUTION OF THE BETA-CHAIN TO T HE ANTIGEN-SPECIFICITY OF AT-CELL RECEPTOR

T cell receptors (TCR) recognize peptides presented by major histocomo patibility complex (MHC) molecules on the surface of cells. Sequence h omology between the variable regions of the T cell receptor and of ant ibodies suggests that similarly-folded domains participate in ligand b inding in both cases. However, most current models assume that both TC R chains (alpha and beta) are required for specific binding, whereas t he heavy chain alone can confer specificity on many antibodies. We hav e therefore constructed chimeric molecules with alpha and beta from tw o different TCR, one restricted by the class II MHC protein, E(k), and the other by the class I MHC, K-d. The beta chain alone was sufficien t for specific recognition of a peptide, Cw3, bound to K-d, but the al pha chain contributed to the overall avidity. These results suggest th at other TCR may recognize their ligands primarily the the beta chain.