BCR and type 1 diabetes mellitus: Evidence that insulin-reactive B cells play a central role in T1D development was demonstrated by diabetes development in 125mAb-transgenic NOD mice in which most (Tg125(H+L)/NOD) or part (VH125Tg/NOD) of the B cell receptor (BCR) repertoire is insulin-reactive, but not in mice that lacked anti-insulin B cells (i.e., VH281Tg/NOD) (31, 32).