[Localization of protease inhibitors in the chorionic villi of the human placenta, by means of the immunoperoxidase technic].

Alpha-1-antitrypsin and alpha-1-antichymotrypsin have been studied in human placentas, from the first trimester to term pregnancy, by immunohistochemical method. Both proteinase inhibitors were localized to the cytoplasm of the villous syncytiotrophoblast, with a decreasing intensity of staining towards term pregnancy. The Hofbauer cells were intensely positive for intracellular alpha-1-antitrypsin and alpha-1-antichymotrypsin at all gestational ages. According to data of the literature we suggest that the existence of the proteinase inhibitors in the placental barrier possibly represents an important part in the defence mechanism of the placenta and may play a particular role in modifying the maternal immune response towards the foetus.