Low-affinity immunoglobulin gamma Fc region receptor IIa (CD32a)

Low-affinity immunoglobulin gamma Fc region receptor IIa (CD32a) is a single-pass type I transmembrane glycoprotein that serves as a key mediator of the humoral immune response by binding the Fc portion of aggregated immunoglobulin G (IgG) [Source: UniProt P12318]. It is widely expressed on myeloid cells, including macrophages, neutrophils, and notably on platelets, where it is the only Fc receptor present [Source: PubMed 21844395]. Unlike other low-affinity Fc receptors, CD32a contains an intrinsic immunoreceptor tyrosine-based activation motif (ITAM) within its cytoplasmic tail, allowing it to directly initiate cellular activation, phagocytosis, and the release of inflammatory mediators upon cross-linking by immune complexes [Source: NCBI Gene 2212]. In clinical pathology, CD32a is heavily implicated in autoimmune diseases such as systemic lupus erythematosus and is the primary driver of platelet activation in heparin-induced thrombocytopenia (HIT) [Source: PubMed 25595774]. The receptor's function is significantly influenced by the H131R genetic polymorphism, which dictates its binding affinity for IgG2 and affects the efficacy of various monoclonal antibody therapies [Source: PubMed 15665055]. Therapeutic targeting of CD32a involves the use of intravenous immunoglobulins to saturate the receptors or small molecule inhibitors like fostamatinib to block downstream signaling through the Syk kinase pathway [Source: DrugBank DB01201].

Other names

FCGR2ACD32CD32aFc-gamma RIIaFcRIIaFCG2IGFR2

Modulation of immune cell activation through competitive binding of IgG Fc regions or inhibition of downstream ITAM-mediated signaling pathways such as the Syk kinase cascade.