The Placental Fcgamma Receptors Studied Using Immune Complexes of Peroxidase

Abstract

Immune complexes of horseradish peroxidase CHRP) and rabbit IgG antibodies 10 HRP were used to study the Fey receptors in normal human placenta. Cryostat sections of placental tissue were incubated with the complexes, and the peroxidase activity was revealed histochemically. The bound complexes were localized to the apical surface of the trophoblasts and endothelial cells of the fetal stem vessels. Binding also occurred within the wall of some fetal vessels, to stromal cells and occasionally to areas corresponding to (he trophoblastic basement membrane. The strongest binding was obtained with immune complexes prepared at slight antigen excess, Eight- to sixteen-fold increased concentration of human and rabbit IgG was needed lo block the binding of immune complexes. Bovine and porcine IgG did not block the binding. Treatment of tissue sections with neuraminidase enhanced the binding activity of the receptors. The technique is very convenient for studies of Fey receptors in tissue. However, unfixed frozen placental tissue was run suitable for ultrastructural studies.