BACK-TRANSPLANTATION FOR SURVIVAL OF THE GRAFT

P1195 Aims: For survival of the transplanted graft after uncontrolable severe rejection or rejection due to withdrawal of immunosuppressive drugs, “back-transplantation” of the graft from the recipient to the donor is invented. In this study, the possibility of the back-transplantation is explored in the animal experimental model. Methods: Hearts of Wistar rats were transplanted heterotopically to F344 rat without any immunosuppressive drugs. After 5, 6, 7 or 8 days, the transplanted heart grafts were harvested from the recipients and back-transplanted to Wistar heterotpopically. After back-transplantation, cyclosporine (CYA), tacrolimus (FK506) or FTY720 were administered to the back-transplanted recipients. The survivals and pathological findings of the back-transplanted grafts were evaluated according to the day of back-transplantation and the drug administered after back-transplantation. Results: Cardiac grafts survived for 6.2 days in the first recipient. After back-transplantation on day 5and 6, all (5/5 and 5/5, respectively) back-transplanted grafts survived well in the second recipients. On the day of back-transplantation, histological findings of the grafts revealed severe vascular rejection, but on 7 day after back-transplantation, they showed mild cellular infiltration. After back-transplantation on day 7, when 4/5 grafts had no beat, but 2/5 recovered beating on day 3 after back-transplantation without any drugs. After back-transplantation on day 7, when 4/5 grafts had no beat, all (5/5) recovered beating well with administration of FTY720 on day 3 after back-transplantation. CYA or FK506 had no effect on the survival after back-transplantation in this condition. Pathological findings revealed no cellular infiltration in the cases of FTY720 and vascular necrosis in the cases of no drug, CYA or FK506. After back-transplantation on day 8, no grafts (0/5) recovered beating with any drugs. Conclusions: The possibility of the back-transplantation was shown. FTY720 may be a potent drug for recovery of the graft after back-transplantation. In the exceptional condition such as uncontrolable severe rejection or rejection due to withdrawal of immunosuppressive drugs, back-transplantation of the graft to the donor should be considered. Immunological study on “back-transplantation” should be promoted.