Fc-epsilon Receptor

Fc epsilon receptor (FcεR) is the Fc receptor that binding immunoglobulin E (IgE). There are two types of FcεRs, called FcεRI (or high-affinity Fc epsilon R, Kd ~1nm) and FcεRII/CD23 (or low-affinity Fc epsilon R, Kd 0.1-1μm). FceRI and FcεRII/CD23 are very different in their molecular structure. FceRI belongs to the immunoglobulin superfamily and is highly homologous in sequence and structure to the IgG Fc receptors, while FcεRII/CD23 is a member of the C-type lectin superfamily. FcεRII/CD23 receptors are expressed on B cells, a variety of innate cell types and epithelial cells. FcεRI receptors are expressed on a variety of cells in addition to mast cells and basophils.A handful of other receptors, including galectin-3, FcγRIIb, FcγRIV, have been documented to interact with IgE.