The persistence of donor-derived leukocytes, which are capable of proliferating, trafficking, and interacting within the recipient tissues, has been proposed as a biological mechanism which facilitates the induction of acquired tolerance after whole organ transplantation.1 Although the details of the intrinsic mechanisms which underlie the bidirectional immune modulation are unknown, it is speculated that augmentation of chimerism will favor graft acceptance and may eventually lead to a drug-free existence.
Rat hind limb contains mature lymphocytes (regional lymph nodes), nonparenchymal tissue (skin and muscle), and vascularized bone marrow, which after transplantation provides a continuous supply of donor-derived progenitor cells. In the present study, we compared the level of chimerism induced experimentally by either vascularized bone marrow transplantation (VBMTx) using the rat hind limb allograft model, or else by infusion of either lymph node or bone marrow cells. Their influence on the incidence and severity of graft-versus-host disease (GVHD) was also assessed.