The A, B and H Blood-Group Antigens in Human Placenta

Thirty human placentas of embryo fetuses of various ABO blood groups and representing all stages of pregnancy between the fifth week (ovulation age) and term were examined for the ABH antigens by immunofluorescence. The trophoblast was consistently negative for both the H and A, B antigens, and the endothelium of the vessels of the chorion, villi and umbilical cord possessed only the basic H structure. The findings contrast with full antigenic complement of the endothelium and of sundry epithelia in the embryo fetus proper, each according to its ABO blood group. The lack of demonstrable ABH antigens in the trophoblast tallies with a similar lack of demonstrable transplantation antigens; it renders the trophoblast unassailable by maternal A, B isoagglutinins.