Dynamics of immunoglobulins at the feto-maternal interface

Transplacental transport of maternal immunoglobulin G (IgG) to the developi ng fetus is extremely important in the protection of the newborn from infec tion. Although the exact mechanisms of the selective and active transfer of IgG across the placental barrier are not fully understood, receptors for t he Fc part of IgG (Fc gamma Rs) in the placenta are believed to play a key role. Several known Fe receptors, Fc gamma RI, Fc gamma RII, Fc gamma RIII and FcRn (neonatal FcR), demonstrate heterogeneous expression patterns in p lacenta. Immunohistochemical analysis shows the expression of Fc gamma RI o n Hofbauer cells in stromal tissue, Fc gamma RII on Hofbauer cells and feta l blood endothelium, Fc gamma RIII on Hofbauer cells and trophoblasts, and FcRn on syncytiotrophoblasts and endothelial cells. Recent studies provide evidence for important associations among these receptors and transcytosis of IgG, as well as scavenger mechanisms for clearing immune complexes in th e placenta during pregnancy.