Prolonged hematopoietic chimerism in normal mice transplanted in utero with human hematopoietic stem cells.

We have previously reported prolonged hematopoietic chimerism in normal mice transplanted in utero with human fetal hematopoietic stem cells (HSC) by flow cytometry. We now further confirm the human origin of these cells by demonstrating human DNA in the marrow of one such chimeric mouse. We also examined 42 mice born after in utero transplantation with HSC enriched from human adult marrow cells. All live-born mice were treated with recombinant human growth factors. Twelve had human cells in the peripheral blood (range: 01.-2.93%). Thymic samples were positive in 3 cases. The bone marrow of 2 mice contained cells expressing human CD34 antigen. Light scatter characteristics support the presence of multilineage hematochimerism. Human IgM was present in 2 of 4 chimeric sera tested. Thus, normal mice transplanted in utero with human HSC may permit long-term engraftment and differentiation of the human HSC.