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 were 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 lymphohematopoietic microchimerism in unrelated primates even without immunosuppression and can alter donor-specific skin graft survival.

Uterine epithelioid leiomyosarcoma in a pig-tailed macaque

During ultrasonographic examination following spontaneous abortion, an approximately 6-cm diameter mass of mixed echogenicity is detected in the uterine wall of a mature pig-tailed macaque (Macaca nemestrina). Grossly, the mass is associated with the uterine fundus, multilobulate and tan with red-black mottled foci on cut surface. Microscopically, the invasive mass is composed of poorly differentiated round cells arranged in sheets and bundles supported by a fine fibrous stroma. On immunohistochemical evaluation, neoplastic cells contain vimentin, desmin, muscle actin, and smooth muscle alpha-actin antigens and do not react with antibodies to low and high molecular-weight cytokeratins. Cell morphology and immunohistochemical results indicate a diagnosis of epithelioid leiomyosarcoma (clear cell variant).