Stimulator cell type influences the response of T cells to staphylococcal enterotoxins.

Responses to the superantigen Mls are characterized by proliferation of a significant percentage of T cells expressing receptors encoded by one or a few V beta gene segments. Apparently similar responses are elicited by the staphylococcal enterotoxins (SEs) and other bacterial superantigens. We have observed that T cells can be stimulated by the bacterial superantigen SEs presented by either spleen cells or fibroblasts transfected with the appropriate MHC class II genes. However, the results in this study showed that T cells required more than 100-fold higher concentrations of SEA in the presence of L cell transfectants than spleen APC, although T cell responses to SEB and several other toxins presented by the two types of APC were equivalent. Thus, L cell transfectants have a selective defect in presenting SEA. These data suggest that fibroblasts lack a component required by SEA to stimulate certain T cells, and lead us to propose an alternative model for bacterial superantigen mitogenesis in which the superantigen binds to and modifies the behavior of an endogenous co-ligand.