Investigation of Antibody-Mediated Rejection in Composite Tissue Allotransplantation in a Rat Limb Transplant Model

Background. Despite the widely accepted implication of antidonor antibodies and complement in solid organ transplantation, their role in reconstructive allotransplantation is not clear. The aim of this study was to analyze the humoral immune response using a rat orthotopic limb transplantation model. Methods. We used the Brown Norway to Lewis rat orthotopic hind-limb transplant model: Group 1, isografts; group 2, allografts with daily continuous cyclosporine treatment to prevent acute rejection; and group 3, allografts undergoing multiple episodes of acute rejection. Samples were taken at 30, 60, and 90 days. Serum was analyzed by FACS for antidonor antibodies. Tissue deposition of antibodies and complement was investigated by immunofluorescence. Results. By day 90, animals in group 3 had undergone 19 (+/- 3.2) acute rejection episodes. There was no difference in the occurrence of serum antidonor antibodies between the three groups at any time point. However, at 90 days, anti-third-party antibodies were significantly greater among group 3. There was no difference in antibody or complement deposition in muscles between the 3 groups. Conclusion. Despite the increased antibody against a third party after multiple rejection episodes in this animal model, there was no clear evidence of an antibody-mediated alloresponse in limb transplantation.