GENE-TRANSFER DIRECTLY DEMONSTRATES A ROLE FOR TCR V-ALPHA ELEMENTS IN SUPERANTIGEN RECOGNITION

Recent structure-function studies of ours and others indicating that r egions of the TCR other than V beta are involved in the TCR-superantig en (SAg)-MHC class II trimolecular interaction were correlative; thus, while the conclusions were persuasive, they were not unequivocal. The transfection experiments described in this report show that 1) respon siveness to staphylococcal enterotoxin B in V beta 6 T cells was trans ferred by a V alpha 4- but not by V(alpha 8- and V alpha 10-containing alpha-chain cDNA constructs, 2) responsiveness was not transferred by a chimeric alpha-chain construct containing the N and J regions from a responsive T hybrid clone and the V alpha 10 V alpha region from a n onresponsive clone, and 3) responsiveness was transferred by a chimeri c alpha-chain construct in which most of the V alpha region (from the N terminus to the C-terminal end of the complementarity-determining re gion 2) was derived from the V alpha 4 alpha-chain of a responsive T h ybrid and the rest (framework 3, N, and J) from the V alpha 8 alpha-ch ain of a nonresponsive T hybrid. Thus, these data provide the first di rect evidence for a specific SAg response facilitating activity in a d efined V alpha segment and map this activity N-terminal of framework r egion 3. Furthermore, the diversity in the alpha- and beta-chain junct ional regions of a panel of staphylococcal enterotoxin B-responsive V beta 6 T hybrid clones excludes a stringent corequirement for a partic ular junctional region for the V alpha 4 segment to mediate its facili tating activity. Finally, a model postulating a universal role for V a lpha elements in TCR recognition of SAg is presented.