V-ALPHA DOMAIN MODULATES THE MULTIPLE TOPOLOGIES OF MOUSE T-CELL RECEPTOR V-BETA-20 STAPHYLOCOCCAL ENTEROTOXIN-A AND ENTEROTOXIN-E COMPLEXES/

The superantigens staphylococcal enterotoxin A and E (SEA and SEE) bot h contact major histocompatibility complex (MHC) class II molecules on two sites located on the alpha and beta chains. We have investigated the role of the T cell receptor (TCR) alpha chain in the modulation of the various topologies of TCR/SEA (or SEE)/class II complexes. For th is purpose, we have used three mouse V beta 20 T cell lines expressing different V alpha domains and two T cell hybridomas expressing mouse V beta 1 or V beta 11 segments. The response of these T cells to SEA a nd SEE was studied in the context of presentation by wild-type human M HC class II molecules; or by mutants on MHC, in each of the two supera ntigen binding sites (position alpha 39K and beta 81H) to which the su perantigens can still bind but with an altered conformation. Although V beta 20 T cell lines are efficiently stimulated using SEA and SEE pr esented by wild-type HLA-DR1 molecules, our results show that the natu re of the TCR V alpha domain can affect differently the recognition of the toxins bound to mutant class II molecules. This suggests that var ious functional topologies exist for both SEA and SEE/class II complex es and that the T cell response to each of these complexes can be modu lated by the V alpha domain of the TCR. Interestingly, the recognition of SEE and SEE is achieved in different fashions by a given V beta 20 T cell line.