Prolonged allogeneic and xenogeneic microchimerism in unmatched primates without immunosuppression by intrathymic implantation of CD34(+) donor marrow cells

Engraftment of stem cell-enriched donor marrow implanted in the thymus of a foreign host might facilitate acceptance of donor-specific organ or tissue grafts, To test this hypothesis, allogeneic and xenogeneic CD34(+) marrow cells from unrelated adult male baboons and humans mere injected intrathymically in eight infant female baboons,:both with and without standard cyclosporine-based immunosuppression, In allogeneic experiments, male (donor) cells, of both T-and B-cell lineages, were detected by PCR in the peripheral blood of all six recipients and persisted for at least 15 months in 2/4 recipients studied longtutudinally, Donor-derived skin grafts survived twice as long as third party grafts in unimmunosuppressed recipients, In xenogeneic protocols, human male (donor) cells were demonstrable for 7 and 15 months, respectively, in two baboon recipients with evidence that implanted human CD34(+) cells had produced lymphoid progeny, Survival of donor-specific skin xenografts was prolonged in one of two recipients, These experiments demonstrate that the intrathymic injection of CD34(+) marrow cells can result in long-lasting lymphohematopoeitic microchimerism in unrelated primates even without immunosuppression and can alter donor-specific skin graft survival. (C) 1997 Academic Press.