The infusion of human fetal liver cells

Only transient engraftment of infused fetal liver cells has been demonstrated in a small proportion of patients with hypoplastic bone marrow or patients undergoing treatment for acute leukemia. This presumably reflects the ability of the recipient to reject the infused cells, the infusion of too few viable stem cells or the availability of too few accessory cells; it is clear from the successful engraftment of infused fetal liver cells in a high proportion of infants and fetuses with severe immunodeficiency diseases that, under favorable circumstances, cells derived from human fetal liver are capable of establishing effective grafts and making a substantial contribution to hematopoiesis comparable to that of transplanted cells derived from the liver of the fetal mouse, rat, rabbit or dog. Significant clinical and hematological improvements have been described following infusions of fetal liver cells without evidence of engraftment. These improvements have been attributed to the ability of the infused cells to promote regeneration of autologous hematopoiesis and to inhibit the growth of tumor cells. These possibilities are worthy of evaluation in relation to the production of putative regulators of cellular proliferation in the liver. Meanwhile a suppressor of tumor growth is being used to purge bone marrow prior to autologous transplantation. The generation in vitro of cells which possess the properties of hematopoietic stem cells generated in the liver--from cells which can be maintained as permanent cell lines--would transform hematopoietic cell replacement therapy, and the possibility may not be too unrealistic to contemplate.