ABSTRACT
Once pregnancy is established, the placenta subjects the mother to alloantigens, for example, paternal major histocompatibility complex, as well as minor H histocompatibility antigens, developmental and sex-linked ones. Most important, pregnancy proceeds successfully during natural or induced aggamma globulinemia. Trophoblasts rely for optimal growth on autocrine and paracrine growth factors. They contain alot of retroviral sequences, and express a high number of oncogenes. In vitro, trophoblasts possess many macrophage-like characteristics, including phagocytosis, easily measurable by the uptake of fluroescent latex beads. The trophoblast outgrowth stopped at the periimplantation phase, in a quite precise time window; there was then no secretion of equine choriononic gonadotrophin (ECG) and the embryos were massively infiltrated by lymphocytes. Pregnancy outcome could be ascertained very early, in fact, by appearance of ECG and detection of trophoblast outgrowth from the conceptus and subsequent attachment.
