Low-affinity immunoglobulin gamma Fc region receptor (FcγR) (FCGR)

The low-affinity immunoglobulin gamma Fc region receptor (FcγR) family consists of several cell surface glycoproteins that bind the constant (Fc) region of IgG antibodies with low to medium affinity (Sino Biological, 2024 [2]). In humans, this group primarily includes the activating receptors FcγRIIA (CD32a), FcγRIIIA (CD16a), and FcγRIIIB (CD16b), alongside the unique inhibitory receptor FcγRIIB (CD32b) (Frontiers in Immunology, 2019 [9]). These receptors are essential for translating antibody-mediated recognition into effector immune responses, such as phagocytosis, antibody-dependent cellular cytotoxicity (ADCC), and the release of pro-inflammatory cytokines (Expert Reviews in Molecular Medicine, 2009 [1]). While activating receptors utilize immunoreceptor tyrosine-based activation motifs (ITAM) signaling to stimulate leukocytes, FcγRIIB employs an inhibitory motif (ITIM) to modulate B-cell receptor signaling and maintain peripheral tolerance (NCBI, 2025 [15]). From a biotech perspective, these receptors are central to the efficacy of most monoclonal antibodies; many drugs are Fc-engineered (e.g., Margetuximab, Obinutuzumab) to enhance their interaction with FcγRIIIA on natural killer cells to maximize tumor lysis (PMC, 2021 [12]). Conversely, agonists or bi-specific agents targeting the inhibitory FcγRIIB are under development for systemic lupus erythematosus and other autoimmune conditions to dampen B-cell hyperactivity (MDPI, 2019 [13]). Genetic polymorphisms within this family, particularly the V158F variant of FCGR3A, serve as critical predictive biomarkers for patient response to therapeutic antibodies in both oncology and inflammatory disease settings (Frontiers in Immunology, 2019 [3]).

Other names

CD16CD32Low-affinity Fc gamma receptorFc-gamma receptor IIFc-gamma receptor IIIFCGR2FCGR3FCGR2AFCGR2BFCGR3AFCGR3BIgG Fc receptor

Therapeutic antibodies engage these receptors to either promote effector cell activation (e.g., ADCC, ADCP) via activating isoforms like FcγRIIIA/CD16a or to suppress immune cell activity and B-cell activation via the inhibitory isoform FcγRIIB/CD32b (Frontiers in Immunology, 2019 [9]; PMC, 2021 [12]).