Abrogation of the allelic exclusion in a T cell receptor beta chain gene transgenic mouse strain.

The expression of endogenous T cell receptor (TcR) beta chains in a TcR beta chain gene transgenic mouse (TGM) strain was examined. Unlike many other TGM strains reported, a considerable proportion of T cells from the thymus and spleen as well as organ cultured fetal thymus from our TGM express endogenous TCR beta chains on their surface. Compatible with this was the elucidation of VDJ rearrangement of endogenous beta chain genes by PCR. Three color flow cytometric analysis of thymus cell subpopulations revealed that the expression levels of both endogenous and transgenic TcR beta genes are regulated in a maturational stage specific manner. Splenic T cells contained a several fold higher percentage of endogenous TcR beta positive cells than thymus cells, suggesting a role of TcR on T cell peripherization. V beta 6 positive cells were deleted in the TGM carrying minor lymphocyte stimulating (Mls)-la antigen, indicating that the endogenous TcR beta is functional in terms of transmitting a signal for clonal deletion.