Table 1.

Expression and major functions of IgE-binding receptors or molecules

Receptors or molecules	Cell typesa	Major functions
FcεRI (αβγγ or αγγ)	Mast38, basophils38, Langerhans38, dendritic38,41, monocytes38, eosinophils38,40, neutrophils39,40, platelets138,139, bronchial epithelial cells of asthmatics45 and airway smooth-muscle cells44,140. In mice: dendritic cells after Sendai virus infection41, neutrophils and eosinophils during Plasmodium infection40 and superior cervical ganglion and myenteric plexus neurons43; in rats: pinealocytes141.	αβγγ: immediate hypersensitivity2, parasite immunity2, enhanced cytokine production and survival in mast cells59 and MCp recruitment in the airway142. αγγ: antigen presentation1,38.
FcεRII (CD23)	B cells143, T cells, NK cells, monocytes, macrophages, follicular dendritic cells143, Langerhans cells, bone marrow stromal cells, neutrophils, eosinophils, platelets1,3,17 and airway20 and intestinal144,145 epithelial cells.	Regulation of IgE production1, killing of intracellular pathogens (Leishmania major146 and Toxoplasma gondii26) or tumor cells28, facilitated antigen presentation1 and transport of IgE and antigens across the epithelium19,144.
FcγRII and FcγIII[AU: OK?](in miceb)	Mast cells147 and macrophages147.	Cell activation147.
FcγRIV (only in mice)	Monocytes, neutrophils and macrophages148,149.	Phagocytosis, cytokine production and antigen presentation in macrophages148,149.
Gelactin-3	Mast cells150,151, basophils150, neutrophils152, monocytes and macrophages153–156, eosinophils157, Langerhans158,159, T160, B161 and dendritic162.	Potentiate FcεRI activation151.

^aThe cell types listed in bold are expressed in both humans and mice.

^bHuman FcγRIII has no affinity for IgE. However, human mast cells and basophils express the immunoreceptor tyrosine-based inhibitory motif–containing receptor, FcγRIIB, which can reduce activation of these effector cells through the FcεRI when it is co-ligated with the FcεRI¹²⁷.