Comparison of Lung and Kidney Allografts in Induction of Tolerance by a Mixed-Chimerism Approach in Cynomolgus Monkeys

Background, We have previously reported the successful induction of renal allograft tolerance in non-human primates using a nonmyeloablative conditioning regimen to produce it mixed-chimeric state in the recipient. In the present study, we applied this same technique to lung allotransplantation in cynomolgus monkeys. Methods. Nine pairs of fully major histocompatibility complex (MHC)-mismatched cynomolgus monkeys were used. The conditioning regimen consisted of total body irradiation, thymic irradiation, and antithymocyte globulin. The recipients underwent lung and bone marrow transplantation, followed by anti-CD154 monoclonal antibody (mAb), and it 1-month course of cyclosporine. The regimen included anti-CD8 mAb in the last 5 recipients and alpha 1-antitripsin in the last 3 recipients. The results were compared with 8 recipients that received kidney allografts using the same regimen. Results. Transient chimerism developed in all lung recipients, as was previously seen in the kidney recipients. Nonetheless, the lung recipients rejected their allografts significant earlier than the kidney recipients (P <.01.). Conclusions. Despite the successful induction of mixed chimerism in recipients of fully MHC-mismatched lung allografts, we have not observed long-term graft survival, as has been seen in an analogous kidney model. Strategies to overcome this problem include organ-specific modifications of the transplant regimen.