Interaction between superantigen and T-cell receptor Vbeta element determines levels of superantigen-dependent cell-mediated cytotoxicity of CD8(+) T cells in induction and effector phases.

Specific superantigens activate different T-cell fractions with distinct TCR V beta elements in association with MHC class II molecules and also induce SDCC against MHC class II(+) target cells. In the present study, to determine whether the responsiveness of each CD8(+) T-cell fraction expressing a different TCR V beta element is primarily determined by the TCR V beta, we compared the levels of proliferation and SDCC in V beta3(+) and V beta11(+) T cells upon stimulation with SEA. Upon stimulation with SEA(wt), the levels of proliferation were higher in V beta3(+) T cells than in V beta11(+) T cells. The levels of SDCC were also higher for the combination of V beta3(+) T cells and SEA(wt) than for the combination of V beta11(+) T cells and SEA(wt) during both the induction phase and the effector phase. In addition, upon stimulation with SEA(m), the levels of proliferation were higher in V beta11(+) T cells than in V beta3(+) T cells. And then, the levels of SDCC were also higher for the combination of V beta11(+) T cells and SEA(m) than for the combination of Vbeta3(+) T cells and SEA(m) during both the induction phase and the effector phase. These results suggest that the SAG-responsiveness of each CD8(+) T-cell fraction expressing a different TCR V beta element is primarily determined by the interaction between the TCR V beta element and the SAG.