THE EXPANSION OF A CD4(-CELL POPULATION BEARING A DISTINCTIVE BETA-CHAIN IN MRL LPR() T)LPR MICE SUGGESTS A ROLE FOR THE FAS PROTEIN IN PERIPHERAL T-CELL SELECTION/

MRL lpr/lpr mice suffer from a systemic lupus erythematosus-like autoi mmune disease. The lpr mutation impairs the normal transcription of th e fas message, the product of which mediates apoptosis and presumably the proper selection of T cells. We have found an early expansion of C D4(+) T cells bearing a distinctive V beta 8.3-D beta 1.1-J beta 1.1 T cell receptor beta chain in the periphery of MRL lpr/lpr mice, which was not detected in MRL +/+ mice nor in the thymus of MRL lpr/lpr mice . Thus, since thymic selection is normal in MRL lpr/lpr mice, we propo se that the lpr mutation results in defective negative selection at th e periphery.