Figure 4.

IgE receptors structure. There are two basic receptors for the IgE molecule: (1) a membrane high-affinity receptor FcεRI (expressed especially on the surface of mastocytes, basophils, smooth muscle cells and dendritic cells in the form of an αβγ₂ tetramer and further and in lesser amounts, on the surface of antigen-presenting cells /dendritic cells, Langerhans cells, monocytes or eosinophils/ in the form of an αγ₂ trimer) and (2) a cellular or soluble low-affinity receptor, FcεRII (CD23, Ca-dependent lectin, first described on the surface of B-lymphocytes and some haematopoietic cells, later also on T-lymphocytes, dendritic cells, eosinophils, platelets, smooth muscle cells or epithelial cells). Receptor transmembrane signalling and subsequent cell activation are mediated by intracellular domains – ITAM (Immunoreceptor Tyrosine-based Activation Motif) that are contained in the intracellular parts of β and γ chains.