Sensitized recipients exhibit accelerated but not hyperacute rejection of vascularized composite tissue allografts

Currently, the donor-recipient matching process for vascularized composite tissue allotransplantation (VCTA) closely follows the standard practices for solid organ transplantation. Sensitization is considered a contraindication to VCTA. However, the role of sensitization in VCTA rejection is largely unstudied.

Major histocompatibility-mismatched ACI (RT1) donors and Wistar Furth (WF) (RT1) recipients were used to determine whether sensitization would lead to hyperacute rejection in VCTA as in other organs, such as kidneys. WF rats were presensitized to ACI antigens by skin transplantation and received heterotopic osteomyocutaneous VCTA flaps. Kidney transplants served as controls.

Production of anti-donor antibody was detected in WF recipients after rejection of the ACI skin grafts. Sensitized WF rats rejected VCTA grafts from ACI rats significantly faster (P<0.05) than unsensitized recipients, but not hyperacutely. Rejection in the sensitized recipients was not prevented by immunosuppression with FK506 and mycophenolate mofetil. In contrast, kidney allografts from ACI rats were hyperacutely rejected within 30 min by sensitized recipients. To confirm the role of antibody-mediated rejection in the sensitized recipients, serum from presensitized rats was adoptively transferred into naïve WF rats. Hyperacute rejection occurred only in transplanted kidneys but not VCTA. Histologic examination of tissues from acceleratedly rejected VCTA showed dense lymphocytic infiltrates, and no antibody deposition.

VCTA are rejected in an accelerated fashion but not hyperacutely in the presence of allosensitization and preformed anti-donor antibody. The rejection of VCTA in sensitized recipients is mainly cell mediated and differs mechanistically from that for renal transplants.