The hypothesis that cell-surface directed antibody may interfere with organogenesis was investigated by means of an experimental system wherein histotypic in vitro reconstruction of chick embryo mesonephros was modified by an heterologous Forssman antibody. The Forssman antigen is expressed at the surfaces of epithelial cells of the duct and collecting tubules in contrast to its absence from the rest of the nephron. Incubation of suspension of dissociated single cells from mesonephroi allows organotypic reconstruction of both F+ and F− elements when normal serum is added to the culture, while anti-F sera inhibit the reconstruction of F+ structures. It is proposed that these experiments reflect a set of circumstances that may occur in viviparous animals where transplacental antibodies are capable of harming the early embryo.

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.