Table 2.

Fc receptors and their potential relevance in epithelial IgG trafficking.

Fc Receptor	Sensitivity to Deglycosylated IgG	Potential Relevance in Epithelial IgG Trafficking	Refs.
FCGR1	Rather insensitive due alternative binding domain.	Has not yet been implicated in IgG trafficking; expression in epithelial has not yet been demonstrated.	[30,32,53]
FCGR2	Endo S treatment of IgG decreases their interaction with FCGR2, but fucose does not alter the affinity to FCGR2.	Expression in epithelial cells from placenta was shown in several studies. Was linked to IgG trafficking of maternal IgG to the fetus in placental cell lines (FCGR2b).	[26,29,32,53,54]
FCGR3a	Endo S treatment abolishes the interaction with FCGR3, but also fucosylated IgGs such as hIgG used here were shown to bind with significantly decreased affinity.	Expression in human nasal epithelium was demonstrated. Controversially discussed for placental IgG trafficking.	[32,53,55,56]