Role of CD23 on epithelial cells in the pathogenesis of food allergic disease.

a | Allergen–IgE complexes are captured by CD23 on the luminal side of the intestinal epithelium and transported into the mucosa, where they bind to FcepsilonRI on mast cells and dendritic cells (DCs), causing allergic inflammation and local IgE class switching in B cells and IgE synthesis (1). This occurs in the fetus by the swallowing of amniotic fluid containing maternal allergen–IgE complexes, and may also represent the mechanism of early sensitization to food allergens in the adult intestinal tract. b | IgE synthesized by plasma cells in the mucosa are transported by CD23 on the mucosal side of the epithelium into the gut lumen, where they capture allergens and bind to CD23 on the luminal side of the epithelium (2) to be delivered to the mucosa. c | Finally, the inflammation caused by allergic reactions mediated by IgE in the mucosa damages the intestinal epithelium, disrupting the tight junctions between the epithelial cells. Free allergens can now pass between the cells and bind to the IgE-sensitized mast cells and DCs in the mucosa, exacerbating the food allergy (3).