CD80 and diabetes mellitus: We further used coinhibiton-deficient PD-1−/−, PD-L1−/− and RIP-B7.1+/PD-L1−/− mice (differing from PD-L1−/− mice only in the tg B7.1 expression in beta cells) to determine whether induction of ppins- and ppinsΔA12–21-specific CD8 T-cell responses and diabetes development depends on specific costimulatory and coinhibitory signals from pancreatic beta cells.