The combination of donor pretreatment with cyclophosphamide, organ culture in 95% O2:5% CO2 for 7–10 days, and short-term immunosuppression of recipients with cyclosporin A (CsA) were necessary to obtain 100% survival of single-cluster BALB/c islet allografts in outbred mice. In vivo and in vitro pretreatment of the donor tissue alone resulted in the acceptance of 45% of the islet allografts in nonimmunosuppressed outbred mice. CsA treatment of recipients alone yielded 40% survival of the untreated allografts. CsA treatment played an important role in maintaining the capacity of islet allografts to function in outbred mice. During CsA treatment, 88% of streptozocin-treated mice showed graft-dependent reversal of diabetes; the remainder showed no evidence of graft function, and CsA treatment failed to prevent acute graft rejection. After withdrawal of CsA immunosuppression, 38% of this total group remained normoglycemic. These findings suggest that modulation of both donor-tissue immunogenicity and recipient responsiveness will be required for successful pancreatic islet transplantation in diabetic humans.

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