Gene transfer directly demonstrates a role for TCR Vα elements in superantigen recognition

Recent structure-function studies of ours and others indicating that regions of the TCR other than Vβ are involved in the TCR-superantigen (SAg)-MHC class II trimolecular interaction were correlative; thus, while the conclusions were persuasive, they were not unequivocal. The transfecfion experiments described in this report show that 1) responsiveness to staphylococcal enterotoxin B in Vβ6 T cells was transferred by a Vα4- but not by Vα8- and Vα10-containing α-chain cDNA constructs, 2) responsiveness was not transferred by a chimeric α-chain construct containing the N and J regions from a responsive T hybrid clone and the Vα10 Vα region from a nonresponsive clone, and 3) responsiveness was transferred by a chimeric α-chain construct in which most of the Vα region (from the N terminus to the C-terminal end of the complementarity-determining region 2) was derived from the Vα4 α-chain of a responsive T hybrid and the rest (framework 3, N, and J) from the Vα8 α-chain of a nonresponsive T hybrid. Thus, these data provide the first direct evidence for a specific SAg response facilitating activity in a defined Vα segment and map this activity N-terminal of framework region 3. Furthermore, the diversity in the α- and β-chain functional regions of a panel of staphylococcal enterotoxin B-responsive Vβ6 T hybrid clones excludes a stringent corequirement for a oarticular iunctional region for the Vα4 segment to mediate its facilitating activity. Finally, a model postulating a universal role for Vα elements in TCR recognition of SAg is presented.