We have noticed that bone marrow transplanted in a vascularized limb graft providing a continuous supply of donor BMC may prolong the survival time of skin graft from the same donor. The question arises whether the raised microchimerism playsa role in the prolonged survival of skin allograft. The aim of the study was to follow the development of microchimerism after allogeneic vascularized bone marrow transplantation (VBMTx) concomitantly with the rejection procesess of transplanted skin. The BN rats served as donors and LEW rats as recipients of VBMTx and free skin flap allograft. Hind limb was transplanted followed by afull-thickness skin graft on the dorsum. Cellular microchimerlsm was investigated in recipients ofVBMTx and skin grafts in blood. spleen, mesenteric lymph node and bone marrow with monoclonal antibody OX27 directed against MHC class I polymorthic RTI on BN cells and quantitatively analysed in FACStar. InVBMTx group free skin flap survived 70 daysafter weaning of CsA.lntravenous infusion of BMC in suspension equivalent to that grafted in hind limb did not prolong skin graft survival after cessation of CsA therapy. Donor-derived cells could be detected in VBMTx recipients as long 70 days after wearing of CsA but not in recipients of Lv. suspension BMC grafting.

Keywords: Tolerance, Allograft, Bone Marrow, microchimerism