Between 12 and 26 wk of age, ∼80% of female nonobese diabetic (NOD) mice from the inbred Sansum colony develop lymphocytic insulitis and become overtly diabetic. The disease in this animal model is similar to human insulin-dependent diabetes mellitus (IDDM) in both genetics and autoimmune pathogenesis. Cyclosporin A (CsA) has been used for immunosuppression in IDDM of recent onset in humans but has several limiting side effects. Therefore, a different regimen for CsA immunosuppression was investigated. Autologous splenic lymphoid cells from 12-wk-old not-yet-diabetic female NOD mice were cultured for 72 h with CsA plus interleukin 2 (IL-2) before reinfusion into the animal from which they were isolated. After this treatment, only 2 (18%) of 11 mice became overtly diabetic during an observation period of 19 wk, while 18 (86%) of 21 age-matched control mice developed diabetes during the same observation period (P < .001). These data suggest an ex vivo preferential IL-2 activation of specific suppressor cells for the autoimmune process with CsA blockade of cytolytic/helper activities. Because the in vivo concentrations of CsA with this procedure would be negligible, these findings have implications for the potential nontoxic use of CsA in human protocols as well.

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