New developments in stem cell transplantation with special reference to the first in utero transplants in humans.

Based on the experience acquired in post-natal liver transplantation since 1974, we recently initiated pre-natal, in utero stem cell transplantation from the human fetal liver. The first two fetuses that we treated had immunodeficiencies, the third one had thalassemia major. Donors and recipients were not matched. The fetal cells were infused in the umbilical vein of the first two patients and injected intraperitoneally into the third one, under ultrasonic visualization. The first patient, born in 1988, has both engraftment of donor cells and reconstitution of cell-mediated immunity. This child, who had bare lymphocyte syndrome, has no clinical manifestation of the disease and he lives normally at home. The second child, born in 1989, has not yet developed a significant reconstitution of immunity although donor cell engraftment has been proven (Y chromosome in this female patient). The third patient has also evidence of donor cell take (Y chromosome in a female patient) but the effect on thalassemia has not yet been fully analyzed (donor hemoglobin present in small quantity). In all 3 cases, no side-effect of any kind developed in the mother nor in the fetus. Several advantages appear to be associated with in utero FLT: increased probability of graft take, ideal isolation of patient (in the uterus), optimal environment for fetal cell development (in the fetal host).