Figure 1.

Transcytosis and recycling of IgGs in the nasal mucosa mediated by the neonatal Fc receptor (FcRn) and structural overview of the mucosa composition. (A) The olfactory mucosa in mammals is composed of a pseudostratified epithelium that contains olfactory sensory neurons (OSN), supporting cells (SUS) and basal cells. The olfactory epithelium is lined by a thick connective tissue, called the lamina propria, containing Bowman’s gland (BG), blood vessels (BV), and neuronal bundles (NB). (B) Structure of immunoglobulin G (IgG) and binding to FcRn. (C) Immunoglobulin G (IgG) is incorporated into polarized cells of the epithelium via pinocytosis. The FcRn binds to the Fc-domain of the antibody in the slightly acidic environment of the early endosome and mediates transcytosis to the basolateral side or recycling of the IgG to the apical side. Transcytosis is shown here from apical (nasal cavity) to basolateral, but the reverse direction was also reported.