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 Tc R beta chain gene transgenic mouse (TGM) strain was examined. Unlike m any other TGM strains reported, a considerable proportion of T cells f rom the thymus and spleen as well as organ cultured fetal thymus from our TGM express endogenous TCR beta chains on their surface. Compatibl e with this was the elucidation of VDJ rearrangement of endogenous bet a chain genes by PCR. Three color flowcytometric analysis of thymus ce ll subpopulations revealed that the expression levels of both endogeno us and transgenic TcR beta genes are regulated in a maturational stage specific manner. Splenic T cells contained a several fold higher perc entage of endogenous TcR beta positive cells than thymus cells, sugges ting a role of TcR on T cell peripherization. V beta 6 positive cells were deleted in the TGM carrying minor lymphocyte stimulating (Mls)1(a ) antigen, indicating that the endogenous TcR beta is functional in te rms of transmitting a signal for clonal deletion.