Limb transplantation in rats: immunosuppression with FK-506.

The efficacy of a new immunosuppressive agent, FK-506, to prevent the rejection of limb transplants was investigated across a major histocompatibility barrier in rats and compared with Cyclosporine. We performed 129 limb transplants between donor ACI rats and recipient Lewis rats. The mean rejection time of the skin component of limb allografts without immunosuppression was 7 days. Animals receiving a 14-day course of Cyclosporine 25 mg/kg had a mean rejection time of 30 days. In contrast, animals receiving a 14-day course of FK506 1 mg/kg had a mean rejection time of 54 days and those receiving a 14-day course of FK-506 2 mg/kg had a mean rejection time of 122 days. Intermittent administration of FK-506 twice weekly further prolonged the mean rejection times to 149 days in animals receiving 1 mg/kg and to 296 days in animals receiving 2 mg/kg.