Low-affinity immunoglobulin gamma Fc receptor IIa (FcγRIIa), IIb (FcγRIIb), and IIIa (FcγRIIIa) (FcγRIIa/b/IIIa)

The low-affinity immunoglobulin gamma Fc receptors (FcγRIIa, FcγRIIb, and FcγRIIIa) are critical components of the immune system that bridge the humoral and cellular immune responses by binding the Fc region of IgG antibodies (PMID: 26013302). FcγRIIa (CD32a) and FcγRIIIa (CD16a) are activating receptors containing immunoreceptor tyrosine-based activation motifs (ITAMs) that mediate phagocytosis and antibody-dependent cellular cytotoxicity (ADCC), respectively (UniProt P12318, P08637). Conversely, FcγRIIb (CD32b) is the sole inhibitory Fc receptor, utilizing an immunoreceptor tyrosine-based inhibitory motif (ITIM) to suppress B-cell activation and inflammatory signaling (UniProt P31994). These receptors are primary targets for therapeutic monoclonal antibodies, which are frequently engineered to enhance affinity for activating receptors like FcγRIIIa to improve anti-tumor efficacy, or to target FcγRIIb for the treatment of autoimmune disorders (PMID: 25617736). Genetic polymorphisms in these receptors, such as the FCGR3A-V158F variant, significantly influence patient response to antibody therapies, making them important biomarkers in clinical oncology (PMID: 25617736).

Other names

CD32aCD32bCD16aFCGR2AFCGR2BFCGR3ALow affinity immunoglobulin gamma Fc receptor II-aLow affinity immunoglobulin gamma Fc receptor II-bLow affinity immunoglobulin gamma Fc receptor III-a

Modulation of immune cell activation through binding of the Fc region of IgG antibodies, leading to either activation (via ITAM-containing FcγRIIa/IIIa) or inhibition (via ITIM-containing FcγRIIb) of immune effector functions.