Donor cell engraftment in recipient lymphoid tissues after rat limb allograft

The movement of cells from a transplanted tissue into the host organs, the so-called systemic chimerism, is a phenomenon known to occur and be associated with the development of immunologic tolerance in allotransplantation cases. The purpose of this study was to identify donor cell engraftment in recipient lymphoid tissues after performing rat hind limb allograft.

Fifty-five whole-limb allotransplantations were performed in sex-mismatched pairs of rats. Syngeneic male Lewis and allogeneic Dark Agouti donors were transplanted to female Lewis recipients. FK506 was used for immunosuppression. Donor male cells could be identified in the recipient female tissues by semiquantitative polymerase chain reaction analysis for a Y chromosome-specific DNA sequence. Chimerism was assessed at 1, 24, and 48 weeks after transplantation.

There was no rejection episode in any of the limb grafts. Although levels of chimerism were highly variable in each lymphoid tissue, a gradual increase was noticed in all during the course of time. At 1 week after the transplant period, only intrasplenic chimerism was at high level (1%) in three groups. At 48 weeks after the transplant, all recipients with allografts showed very high level (10%) of chimerism in the bone marrow. Two, two, and two of six recipients showed very high levels in the spleen, lymph node, and liver, respectively, at 48 weeks. Intrathymic chimerism was higher at 24 weeks after transplant rather than at 48 weeks.

We demonstrated donor cell engraftment into recipient lymphoid tissues after successful whole limb transplantation. We conclude that limb allograft can work as a vascularized carrier for the bone marrow transplantation, provide a continuous source of donor cells and contribute to chimerism in the recipient.