Induction of specific tolerance in rabbits by kidney allografting and short periods of cyclosporin-A treatment.

A short period of daily treatment with cyclosporin A (25 mg/kg orally or 18 mg/kg by intramuscular injection) induced specific tolerance lasting more than 12 months in 60% of nephrectomised rabbits allografted with one kidney. Tolerant rabbits accepted second kidney and skin allografts from the original donor even though all immunosuppressive therapy had been withdrawn at least 70 days earlier, while third party allografts were rejected normally. These results strongly support the hypothesis that cyclosporin A induces operational tolerance to antigens in a donor-specific, not tissue-specific fashion.