Factors of the extrinsic pathway of blood coagulation in fetal placental macrophages

Term human placentae were examined to identify and localize the factors contributing to extravascular fibrin formation. In addition to blood vessels, components of the extrinsic coagulation cascade were also demonstrated in intracellular localization. These cells in double and treble labeling systems expressed macrophage marker antigens, recognized by DAKO antimacrophage, RFD7, Amersham antimacrophage, and KiM7 monoclonal antibodies and showed positivity for alpha-naphthyl-acetate-esterase (ANAE). The fact that factors of the extrinsic coagulation system can be demonstrated in fetal macrophages of the chorionic stroma suggests that their role is not restricted to cellular defense and phagocytosis, but they may be involved in extravascular intraplacental fibrin formation as well.