Prolonged survival of composite facial allografts in non-human primates associated with posttransplant lymphoproliferative disorder.

BACKGROUND: Composite tissue allotransplantation may have different immunosuppressive requirements and manifest different complications compared with solid organ transplantation. We developed a non-human primate facial composite tissue allotransplantation model to investigate strategies to achieve prolonged graft survival and immunologic responses unique to these allografts.
METHODS: Composite facial subunits consisting of skin, muscle, and bone were heterotopically transplanted to mixed lymphocyte reaction-mismatched Cynomolgus macaques. Tacrolimus monotherapy was administered via continuous intravenous infusion for 28 days then tapered to daily intramuscular doses.
RESULTS: Five of the six animals treated with tacrolimus monotherapy demonstrated rejection-free graft survival up to 177 days (mean, 113 days). All animals with prolonged graft survival developed posttransplant lymphoproliferative disorders (PTLD). Three animals converted to rapamycin after 28 days of rejection of their allografts, but did not develop PTLD. Genotypic analysis of PTLD tumors demonstrated donor origin in three of the five analyzed by short-tandem repeats. Sustained alloantibodies were detected in rejecting grafts and absent in nonrejecting grafts.
CONCLUSIONS: Tacrolimus monotherapy provided prolonged rejection-free survival of composite facial allografts in a non-human primate model but was associated with the development of a high frequency of donor-derived PTLD tumors. The transplantation of a large volume of vascularized bone marrow in composite tissue allografts may be a risk factor for PTLD development.