The limited efficacy of cyclosporine in preventing rejection and graft-versus-host disease in orthotopic small bowel transplantation in rats.

The effect of different schedules of cyclosporine treatment on the survival of small bowel allografts was studied in rats. The administration of a short course of CsA (15 mg/kg on days 0, 1, 2, 4, and 6) had no beneficial effect on graft-vs.-host disease and survival time of the recipient compared with untreated controls. CsA, 25 mg/kg for 1 or 2 weeks prolonged survival significantly (38.3 +/- 3.8 and 42.5 +/- 2.7 vs. 16.6 +/- 2.7, P less than 0.01). When combined with maintenance therapy, 15 mg/kg of CsA 3 times weekly until day 100, only 7 of 30 rats survived more than 100 days. In addition, GVHD was not consistently abrogated in these groups. Only high doses of CsA (25 mg/kg on days 0-6, 15 mg/kg on days 7-13, followed by maintenance therapy) could prevent the onset of GVHD, although the survival time of the transplants was not prolonged compared with untreated controls due to a toxic side effect of CsA on the transplants. It can be concluded that CsA used as monotherapy is ineffective in consistently ameliorating GVHD and rejection in the WAG-BN rat model. This model exhibits at least some of the immunological problems seen in large animal models and can be useful in studying combinations of immunosuppressive drugs or methods that may be applicable to small bowel transplantation in man.