Immunoglobulin epsilon Fc receptor II (CD23 (also commonly FcεRII or FCER2))

Immunoglobulin epsilon Fc receptor II, commonly known as **CD23**, is a low-affinity receptor for IgE that plays a major role in the regulation of IgE responses and B-cell biology[1][5][7]. CD23 is a C-type lectin molecule expressed mainly on mature B cells, activated macrophages, and certain other immune cells[1]. It regulates antigen presentation, facilitates IgE-antigen complex transport, and modulates B cell differentiation[1][2][7]. There are two isoforms, CD23a and CD23b, with distinct expression profiles[1]. CD23 is clinically significant as a diagnostic marker (especially in chronic lymphocytic leukemia) and as a modulator in allergic diseases due to its involvement in IgE regulation[1][2]. While no approved therapies target CD23 directly, modulation of the IgE axis (such as with omalizumab) can impact its function[2]. Safety concerns include immune alterations if CD23 function is excessively inhibited or activated[2][4].

Other names

CD23Fc epsilon receptor IIFcεRIIFCER2Low affinity immunoglobulin epsilon Fc receptor

Modulating IgE levels by interfering with IgE binding or CD23 expression (e.g., anti-IgE therapies like omalizumab block IgE-FcεRI, indirectly affecting CD23-mediated functions) Suppressing or enhancing immune responses through signaling pathways impacting B cell activation and IgE feedback regulation