The neonatal Fc receptor is a protein that in humans is encoded by the FCGRTgene.
The neonatal Fc receptor is an Fc receptor which is similar in structure to MHC class I. It was first discovered in rodents as a unique receptor capable of transporting IgG from mother's milk across the endothelium of newborn rodent's gut. Further studies revealed a similar receptor in humans. In humans, however, it is found in the placenta to help facilitate transport of mother's IgG to the growing fetus and it has also been shown to play a role in monitoring IgG turnover.
There is also evidence that this receptor also plays a role in adult salvage of IgG through its occurrence in the pathway of endocytosis in endothelial cells. Fc receptors in endosomes bind to IgG internalized through pinocytosis, recycling it to the cell surface and preventing it from undergoing lysosomal degradation. This mechanism may provide an explanation for the greater half-life of IgG in the blood compared to other isotypes.