MHC Bias of Mls-1 Recognition Is Not Influenced by Thymic Positive Selection

In contrast to T cell recognition of conventional peptide/MHC, T cell recognition of superantigen is not MHC-restricted. However, an influence of MHC polymorphism on specificity is consistent with accumulating data suggesting a TCR/MHC interaction during T cell recognition of superantigen. We have previously shown that T cells from Vβ8.1 β-chain transgenic mice show an unexpected bias against recognition of Mls-1 presented by H-2dspleen cells. In the current studies we have examined whether thymic positive selection in H-2dmice, which selects T cells that see conventional antigen preferentially in the context of H-2d, is able to overcome the strong bias against recognition of Mls-1/H-2d. The data show that transgenic T cells from both H-2dand H-2kmice have comparable reactivity. The failure of thymic positive selection to overcome the bias against Mls-1/H-2dsuggests that the orientation of the putative TCR/MHC interaction during recognition of Mls-1 is not the same as during recognition of conventional peptide/MHC.