Biological effects of bone marrow in transplanted limb--a review

Transplantation of a vascularized limb should be considered as a double graft: composite parenchymatous non-lymphoid tissue (skin, subcutaneous tissue, muscles, nerves and bones in a block) and bone marrow (BM) tissue. Ready-to-function BM releases mature and precursor cells migrating to the recipient tissues immediately after transplantation. Donor BM-derived cells home to recipient BM cavities and lymphoid organs (LO) and to lesser extent to the non-lymphoid tissues. Interestingly, no acute and subacute graft-versus-host reaction develops. Cellular microchimerism is detected with the presence of donor cells in recipient tissues, at least as long as the transplanted limb is not rejected. Free donor DNA appears in high concentrations in recipient tissues at the time of rejection. The biological significance of the cellular and DNA microchimerism is not clear. Slight prolongation of limb and free-flap skin grafts survival time may be attributed to microchimerism. The beneficial and unwanted effects of transplanted BM tissue should be taken into consideration in the clinical limb transplantation programme. Long-term experimental and clinical observations will allow to draw more clinically applicable conclusions. Abbreviations used in this review: BM: bone marrow, BMC: bone marrow cells, BMTx: bone marrow transplantation, il-BMTx: in limb-bone marrow transplantation, iv-BMCTx: intravenous isolated bone marrow cell transplantation, MLN: mesenteric lymph node, SPL: spleen, LO: lymphoid organs, PHA: phytohemagglutinin, ConA: concavalin A, PWM: pokeweed mitogen, CsA: cyclosporin A, TBI: total body irradiation.