Blood group Rh-D factor in human trophoblast determined by immunofluorescent method

The chorionic villi of human placentas, 12 to 40 weeks' gestation, were examined for Rh-D blood group antigens with a direct immunofluorescent (IF) technique. Specific IF-standing was shown on the plasma membrane and cytoplasm of the villous trophoblasts. This staining decreased in intensity as the placenta matured. In addition, the trophoblasts of hydatidiform and destructive moles were also examined. The intensity of the IF-staining in these trophoblastic tumors was about the same as that in the young trophoblasts of the first trimester of pregnancy.