Donor leukocyte migration following extremity transplantation in an experimental model.

In an effort to further define the immunologic mechanisms leading to acute composite-tissue allograft rejection, the migratory patterns of donor leukocytes were evaluated. Using a rat model, 52 orthotopic vascularized hindlimb transplants were performed in strains representing major histocompatibility mismatches. In order to evaluate the effect of allogeneic skin on limb rejection, all donor skin was removed in a second group of allografts. Recipient lymphoid organs were examined during the week following transplantation for antigen-presenting cells using a donor-specific class II monoclonal antibody. Donor leukocytes, with dendritic cell morphology, were identified in recipient spleen and lymph nodes draining the allograft. Significantly higher numbers of donor leukocytes were present during postoperative days 1 through 4 for both groups. Association of these important passenger leukocytes with host T-lymphocytes may represent the site of initiation of the immune response.