Hematopoietic chimerism in sheep and nonhuman primates by in utero transplantation of fetal hematopoietic stem cells.

Bone marrow transplantation to reconstitute defective hematopoietic cell lines in children with congenital defects is limited by donor availability, graft rejection, and graft-versus-host disease (GVHD). These problems can be eliminated by transplanting normal preimmune fetal hematopoietic stem cells (HSC) into an unrelated preimmune fetal recipient. We show here that injections of allogeneic fetal stem cells into preimmune fetal lambs and monkeys result in long-term stable hematopoietic chimerism. HSCs harvested from the livers of preimmune fetal sheep and monkeys when injected into the peritoneal cavity of young unrelated fetal sheep and monkey recipients results in stable, long-term postnatal hematopoietic chimerism involving lymphoid, erythroid, and myeloid cells of donor origin. Donor cell engraftment was achieved without the use of cytoablative procedures and without the development of GVHD.