Human Amnion as a Model for IgG Transport

Abstract

The ability of fresh human amnion to bind and internalize horseradish peroxidase-labeled IgG (IgG-HRP) was examined in an in vitro Ussing chamber system. The amnion demonstrated unique cell membrane receptors for the Fc portion of IgG molecules (Fc gamma R). The Fc gamma R exhibit exquisite specificity and affinity for IgG monomers as demonstrated by staining with labeled IgG. Labeled IgA, IgM, F(ab')2 fragments of IgG, aggregated IgG, and antigen-antibody complexes all failed to bind to the amnionic epithelial cells. Binding was only minimally affected by changes in ionic strength or pH when viewed at the light microscopic level. The Fc gamma R are located on both the apical and basal cell membranes. The binding of IgG-HRP to the amnion cell membrane was detectable within 1 min, and internalization of the ligand occurred within 5 min. No binding of IgG-HRP was observed following treatment of the membrane with 0.25% trypsin for 30 min at room temperature. Incubation of the amnion at 4 degrees C or in the presence of colchicine or cytochalasin D prevented internalization of the IgG-HRP. These experiments demonstrate Fc gamma R on human amnionic epithelial cells that both bind and internalize IgG, thus allowing the amnion to be used as a model system for studying IgG transport.

Intrauterine Growth Restriction Caused by Underlying Congenital Cytomegalovirus Infection

“…Infection with bacterial pathogens could cause additional complications leading to inflammation [10,11]. Amniotic epithelial cells could also express IgG receptors that could internalize antibody-virion complexes [47]. In this regard, we measured HCMV-specific IgG in amniotic fluid from seropositive mothers and confirmed that amniotic epithelial cells express the neonatal Fc receptor, TLR2, and TLR4 in vitro (unpublished observations), suggesting these molecules could contribute to virion clearance, reduce inflammation, and delay the rupture of fetal membranes.…”

Autophagy and endocytosis in the amnion

“…In early reports, nutritional material, fluid, or particles were transported into cells by absorption through the microvilli, intercellular junctions, and plasma membranes, depending on permeability characteristics. Then pinocytosis and endocytosis were described to play important roles (Bautzmann and Schroder, 1958;King, 1978;Enders, 1981;Stone et al, 1987). Recently, in addition to reporting on endocytosis, we were the first to report on autophagy in amniotic epithelia.…”