Receptors on T cells escaping superantigen-mediated deletion lack special beta-chain junctional region structural characteristics.

The TCR V beta element is pivotal for superantigen recognition; however, not all T cells bearing a particular V beta element respond to an individual superantigen. Recent evidence has indicated that the TCR V alpha element also contributes to recognition of superantigen/MHC class II complexes. To determine whether the TCR beta-chain junctional regions influence recognition of a superantigen encoded by mouse mammary tumor virus (MMTV) proviral integrant Mtv-1, we have analyzed these regions in T cells that have survived superantigen-mediated negative selection in B10.BR-Mtv-1 mice. Our data indicate: 1) no TCR J beta skewing, 2) no difference in the length of the third complementarity-determining region (CDR3), and 3) no outstanding structural features that are shared among the junctional regions of the V beta 3+ T cells that escape thymic clonal elimination in superantigen-expressing mice. Several possible models for TCR engagement of viral superantigen/MHC class II complexes are discussed.