EXPRESSION OF COMPLEMENT REGULATORY PROTEINS ON FETAL BLOOD-CELLS IN-UTERO

Since the fetus is semiallogenic to the mother, mechanisms have evolve d to protect fetal tissue from the maternal immune response. Among the se mechanisms is the expression of cell-surface complement regulatory proteins at the maternal-fetal interface. However, beginning in the th ird trimester, fetal blood cells are exposed to actively-transported I gG antibody. Thus, we speculated that fetal blood cells would require expression of one or more complement regulators by the early third tri mester. Using now cytometry and Western blots, we have demonstrated th e presence of three important complement regulatory proteins in the ci rculating blood cells of human fetuses. These findings are consistent with the putative biological role of the cell-surface complement regul atory proteins.