Low affinity immunoglobulin gamma Fc region receptor II-a (CD32a) (FCGR2A)

Low affinity immunoglobulin gamma Fc region receptor II-a (CD32a), encoded by the FCGR2A gene, is a crucial activating receptor expressed on the surface of myeloid cells and platelets (UniProt P12318). It contains an internal immunoreceptor tyrosine-based activation motif (ITAM) that, upon cross-linking by the Fc portion of IgG, initiates signaling cascades leading to phagocytosis, degranulation, and the release of inflammatory mediators (NCBI Gene ID 2212). In therapeutic contexts, particularly with Intravenous Immunoglobulin (IVIG), the interaction between the Fc fragments of pooled IgG and FcγRIIA is leveraged to treat autoimmune and inflammatory disorders (PMID: 25607457). IVIG acts by saturating these receptors to prevent the destruction of opsonized cells, such as platelets in immune thrombocytopenia, and by modulating the overall threshold of immune activation. A significant genetic variant, the H131R polymorphism, alters the receptor's affinity for IgG2 and is a key determinant in disease susceptibility and the efficacy of immunoglobulin-based therapies (PMID: 10657206). Safety concerns include the potential for platelet activation leading to thrombosis, especially in patients with high titers of immune complexes (PMID: 22535244).

Other names

CD32aFc gamma receptor IIAFCGR2AFCG2IGFR2CD32

Competitive inhibition of pathogenic autoantibody binding to Fc receptors, modulation of ITAM-mediated signaling, and clearance of circulating immune complexes (PMID: 25607457).