This study investigates the effectiveness of FK-506, a new immunosuppressive agent for in preventing the rejection of limb allo-transplants in rats.

Inbred strain Lewis (RT1l) were used as donors and Brown Norway (RT1n) as recipients for limb allotransplan-tation. The experimental animals were divided into four groups; group I: untreated allografts, group II: allografts receiving FK-506 1mg/kg/day for 5-12 days (n=6), group III: 2 mg/kg/day for 15 days (n=6), group IV: single dose of 10 mg/kg (n=3), immediately. Rejection signs, mean survival time of limbs and histologic analysis (by the muscle grading system of Buttemeyer et al.) were evaluated.

The mean survival time in group I was 3.5 ±1.04 days, in group II 7.17 ±3.43 days, in group III 25.5 ±12.01 days and in group IV 16.33 ±8.08 days. FK-506 prolonged the survival time of limbs significantly in a dose-dependent manner. Histologic examination revealed that group II was grade II (n=2) and grade III (n=1); group III was grade I (n=2); and group IV was grade I (n=1) and grade II (n=1).

These results demonstrate the unique effects of FK-506 upon preventing graft rejection and prolonging limb survival allo-grafts in rats.