We are working on developing better treatments for patients with genetic stem cell disorders. Our strategy is to treat fetuses before birth with stem cell transplantation in order to induce tolerance to the foreign transplanted cells and avoid immunosuppression. We have noted that the mother’s immune system is involved in rejecting the cells that are transplanted into the fetus and are now studying how the fetal immune system responds to the transplant. We have also examined whether the fetus becomes sensitized or tolerant to these maternal cells after surgery and have made the surprising discovery that the fetal immune system also becomes activated after pregnancy complications.