BB/Wor rats develop spontaneous autoimmune diabetes similar to human insulin-dependent diabetes mellitus. A T-cell–mediated pathogenesis for BB/Wor diabetes is indicated because disease is prevented by neonatal or adult thymectomy and treatment of diabetes-prone rats with monoclonal antibodies directed against CD5 or CD8 T-cell surface markers. Disease can be adoptively transferred with injections of concanavalin A–activated spleen cells from either acutely diabetic or RT6.1 T-cell–depleted diabetes-resistant BB/Wor rats. We used microbial superantigens to stimulate spleen cells from RT6.1 T-cell–depleted diabetes-resistant rats and demonstrated that such cells activated with staphylococcal enterotoxins (SEs) can also transfer diabetes. The diabetogenic effector T cells are readily activated by SEA, SEC3, and SEE, whereas SEB- and SEC2-activated cells are far less effective in the adoptive transfer of diabetes. These results demonstrate that microbial superantigens are capable of activating self-reactive and diabetes-inducing T cells in vitro in the BB/Wor rat. Ubiquitous microorganisms may be the environmental trigger for autoimmunity in susceptible individuals.

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