Indefinite survival of rat parathyroid allografts without postoperative immunosuppression

Methods that avoid long-term immunosuppression must be developed for human parathyroid allotransplantation to be feasible. Pretransplant treatment of the graft to eliminate passenger cells is one such method. An alternative approach is short-term treatment of the recipients with cyclosporine (CsA). In this study, parathyroid glands from Lewis X Brown Norway rats were cultured for 1 week and treated with antiserum directed against class II major histocompatibility complex antigens. Treated glands were transplanted into hypocalcemic Wistar-Furth recipients that previously received 30 mg/kg of CsA once a day for 3 days before transplantation. At 280 days after transplantation, 67% of the recipients had functional parathyroid allografts. Control rats (no CsA; fresh, untreated glands) rejected these grafts within 28 days. Control rats given 3 days of CsA and transplanted with fresh, untreated glands had functional grafts for greater than 56 days (median survival, 80.5 days). Prolongation of allograft survival with short-term, preoperative CsA demonstrates the efficacy of immunosuppression given at the time of antigen presentation. This course of CsA is even more effective when the recipient receives a graft whose passenger cells are eliminated.