Class I and class II MHC gene products differentially affect the fate of V beta 5 bearing thymocytes.

We have previously shown that T cells bearing V beta 5+ T-cell receptors (TCRs) are frequent in B10 (H-2b) and B10.Q (H-2q) mouse strains but are rare in the congenic strain B10.BR (H-2k). Furthermore, we have found that V beta 5 bearing T cells appear to be excluded from the B10 alloresponse to I-Abm12 despite the participation of most other V beta bearing cells. To further study MHC effects on V beta 5 expression, we have generated two V beta 5 specific monoclonal antibodies and show here that V beta 5 expressing T cells are clonally deleted from strains expressing a class II, I-E molecule. Furthermore, I-E- strains generate few CD4+ V beta 5+ T cells despite significant numbers of V beta 5+ T cells in the CD8+ subset. Thus, V beta 5 bearing T cells are positively selected by class I MHC molecules, clonally deleted by class II I-E molecules, and poorly selected by class II I-A molecules.