Activation of T cells by superantigen in class II-negative mice.

The ability of the staphylococcal enterotoxins to stimulate T cells has been thought to depend on their association with class II MHC products. Here, we demonstrate that a subgroup of staphylococcal enterotoxins, which includes staphylococcal enterotoxin C and staphylococcal enterotoxin E, stimulates strong MHC-independent responses, thereby resulting in T cell expansion and generation of CTL. The immunologic consequences of MHC-independent activation of T cells by superantigens differ from those of class II-dependent activation, inasmuch as this pathway does not result in detectable T cell deletion. These findings delineate a novel MHC-independent T cell activation pathway that leads to both clonal expansion and expression of CTL effector function in response to a subgroup of bacterial superantigens.