Prolongation of rat islet allograft survival by the immunosuppressive agent leflunomide.

The purpose of this study was to investigate the effect of Leflunomide (Lef), alone or in combination with a suboptimal dose of cyclosporine (CsA), on rat allogeneic islet transplantation. Two thousands islets were transplanted under the left kidney capsule of a streptozocin-induced diabetic Lewis recipient. In the ACI to Lewis combination, the mean survival time (MST) of the untreated group was 5.2 +/- 0.8 days. Lef at 2.5, 5, and 10 mg/kg/day for 14 days significantly prolonged MSTs to 19.0 +/- 1.6, 29.8 +/- 3.7, and 29.0 +/- 5.3 days (P<0.01), respectively. CsA at 5 mg/kg/day also prolonged graft survival to 21 +/- 3.5 days. When CsA (5 mg/ kg/day) was combined with Lef (5 or 10 mg/kg/day) and administered for 14 days, the survival rate of the islet allografts was further increased to 34.8 -/+ 4.7 and 36.0 -/+ 6.6 days, respectively. When Lef or CsA monotherapy was extended to 28 days at a dose of 5 mg/kg/ day, MSTs were further increased to 45.8 -/+ 8.8 or 37.4 -/+ 4.7 days, respectively. Graft MST was 56.4 -/+ 9.9 days when Lef and CsA combination therapy was administered for 28 days. In the Brown-Norway to Lewis combination, MST of the allogeneic islets in untreated rats was 6.2 -/+ 0.8 days. When Lef or CsA alone, at 5 mg/kg/day, was administered for 28 days, two of seven Lef-treated rats remained normoglycemia for more than 100 days. Graft survival longer than 100 days occurred in one of five CsA-treated rats, and in five of eight rats treated with the combination of Lef and CsA. The graft-bearing left kidney was removed after 100 days in rats with functional islet allografts, and a second Brown-Norway islet graft was transplanted into the right kidney. In all recipients, the second graft was rejected by 9.8 -/+ 1.5 days. In summary, our findings demonstrate that Lef prolonged allogeneic islet graft survival, and its immunosuppressive effect was improved when combined with CsA.

Duke Scholars

Author John Wiley Williams Jr. Medicine, General Internal Medicine