The immunocytochemical location of two membrane-associated placental tissue proteins in human and cynomolgus monkey placentae.

Using the PAP technique, the location of two new membrane-associated placental tissue proteins, MP1 and PP4 was studied in the placenta, its membranes, decidua and umbilical cord of human and cynomolgus monkeys. The results were the same throughout pregnancy. MP1 was located in the syncytiotrophoblast and trophoblastic cells of the reflected chorion. Other placental tissue components (cytotrophoblast, amnion, decidua, and umbilical cord) were negative. At present, MP1 appears to be specific for trophoblast. PP4 was located in the syncytiotrophoblast. Furthermore clear positive staining for PP4 was found in the villous cytotrophoblast, reflected and basal chorion, amnion, umbilical cord and decidua. In addition, PP4 was positive in some granulocyte-like blood cells in the intervillous space. Immunocytochemically, the most positive staining for both proteins was observed in the membrane of villous syncytiotrophoblastic cells. The findings in the placenta of cynomolgus monkeys were similar to those in women. The monkey could, thus, serve as a model for the investigation of these new membrane-associated placental tissue proteins.