Abstract
During human pregnancy, maternal IgG is transported across the placenta to the fetus. On the way, some maternal antibodies against fetal antigens are removed as immune complexes. The placenta contains several known Fc receptors and also other proteins that bind immunoglobulins. A consideration of the binding properties and distribution of these proteins suggests that the neonated Fc receptor (FcRn) transports IgG across the syncytiotrophoblast, and possibly the fetal blood vessel endothelium. FcγRI, FcγRII and FcγRIII on Hofbauer cells in the stroma probably clear immune complexes, together with FcγRII on endothelial cells.