EVIDENCE FOR ENGRAFTMENT OF HUMAN BONE-MARROW CELLS IN NON-LETHALLY IRRADIATED BABOONS

Background. Prior to organ harvesting, an attempt was made to modulate the donor's immune responses against prospective xenogeneic recipient s by infusion of ''recipient-type'' bone marrow, Methods. For this pur pose, baboons conditioned with total lymphoid irradiation were given 6 x10(8) unmodified human bone marrow cells/kg body weight with no subse quent treatment. Results. Animals survived until they were euthanized at 18 months, Using primers specific for human chorionic gonadotrophin gene, the presence of human DNA was confirmed by polymerase chain rea ction in the blood of one animal for up to 18 months after cell transp lantation; in the other animal, xenogeneic chimerism became undetectab le in the blood at 6 months after bone marrow infusion. However, tissu e samples obtained from both animals at the time they were euthanized had evidence of donor (human) DNA. Additionally, the presence of donor DNA in individually harvested colonies of erythroid and myeloid linea ges suggested that infused human bone marrow cells had engrafted acros s the xenogeneic barrier in both baboons, Conclusions. Bone marrow tra nsplantation from human to baboon leads to establishment of chimerism and modulation of donor-specific immune reactivity, which suggests tha t this strategy could be reproducibly employed to create ''surrogate'' tolerogenesis in prospective donors for subsequent organ transplantat ion across xenogeneic barriers.