Tacrolimus enhances the immunosuppressive effect of cyclophosphamide but not that of leflunomide or mycophenolate mofetil in a model of discordant liver xenotransplantation.

L EFLUNOMIDE (LEF), which suppresses both T and B cells, prolongs survival of heart xenografts in the concordant hamster to rat animal model. l However, xenotransplantation across discordant barriers is the most likely approach to solve the problem of organ shortage. By perfusing guinea pig livers with University of Wisconsin solution containing sodium nitroprusside, we have solved the problem of poor reperfusion of this organ when transplanted into rats.2 Accordingly, we tested the effect of LEF alone or in combination with tacrolimus (PK.) on survival of guinea pig to rat liver xenografts. Results were compared with those obtained following the use of cyclophosphamide (CyP) and mycophenolate mofetil (MMF).