Noncanonical placental Fc receptors: What is their role in modulating transplacental transfer of maternal IgG?
Fig 1
The distribution of Fc receptor expression in placental villous trees.
Maternal IgG present in the intervillous space crosses through distinct cell barriers, including syncytiotrophoblasts, the villous stroma which contains Hofbauer cells and fibroblasts, and fetal endothelial cells. Placental FcRn and FcγRIIIa are expressed in the outermost cell barrier of the villous tree: the syncytiotrophoblast. Hofbauer cells located in the villous stroma express FcγRI, FcγRIIb, and FcγRIIIa. Fetal endothelial cells express FcγRIIb but not FcRn. Fc, Fragment crystallizable; FcRn, Fc receptor neonatal; FcγRI, Fragment crystallizable gamma RI; FcγRIIb, Fragment crystallizable gamma RIIb; FcγRIIIa, Fragment crystallizable gamma RIIIa; IgG, Immunoglobulin.