Background: To date, over 40 in utero transplants have been performed in humans; the only successes were documented in the treatment of severe combined immunodeficiency syndromes. Hemoglobinopathies and metabolic disorders are candidate diseases for this approach; however, when applied clinically, the results have been discouraging. To address the role of the fetal immune system in the outcome of in utero transplantation, we have developed a murine model of in utero transplantation in immunologically intact murine recipients and have studied chimerism and tolerance/immunity to allogeneic donor cells through the lives of the animals.

Methods: We have performed experiments in which purified murine sca-1+/lin- cells and c-kit+/lin- cells of C57BL/6 (H2b) mice were injected into Balb/c (H2d) fetal recipients at early gestational ages.