Porosity of the Placenta to Maternal Cells in Normal Derived Mice

Abstract

THE placenta in mammals has been assumed to act as an anatomical barrier separating the foetus from normal maternal immunological mechanisms and preventing rejection of the foetus, which is in fact normally an allograft¹. There have been a few reports of an occasional maternal cell noted in a newborn infant; however, the significance of this has largely been ignored. We recently showed that maternal cells are present in young mice derived by ovum transplantation². The maternal cells were identified by the presence of a chromosome marker, but the question still remained as to whether the chimaeras resulted from the surgical procedure of ovum transplantation. We have now examined normally derived animals for the presence of foreign maternal cells.