Immunoglobulin Fc gamma receptor (FcγR)

Immunoglobulin Fc gamma receptor (FcγR) is a family of cell-surface receptors that specifically bind the Fc region of immunoglobulin G (IgG) antibodies. These receptors are expressed on various immune cells, including macrophages, neutrophils, natural killer cells, B cells, and mast cells, and serve as a critical link between humoral and cellular immunity[4][10]. FcγRs are classified into three main types based on structure and affinity: FcγRI (CD64, high affinity), FcγRII (CD32, low affinity), and FcγRIII (CD16, low affinity)[4][6]. FcγRI can bind monomeric IgG, while FcγRII and FcγRIII primarily recognize immune complexes. Upon IgG binding, activating FcγRs (FcγRI, FcγRIIA, FcγRIIIA) trigger intracellular signaling via immunoreceptor tyrosine-based activation motifs (ITAMs), leading to phagocytosis, ADCC, and cytokine release[1][5][7]. Inhibitory FcγRIIB contains an immunoreceptor tyrosine-based inhibitory motif (ITIM) that downregulates immune responses[6]. FcγRs play essential roles in host defense against infections, contribute to the pathogenesis of autoimmune and inflammatory diseases, and are important targets for therapeutic antibody engineering to enhance or modulate immune effector functions[3][10].

Other names

Fc receptorFc gamma receptorFcRCD16 (FcγRIII)CD32 (FcγRII)CD64 (FcγRI)

Activation of immune effector cells (phagocytes, NK cells) via ITAM signaling; Inhibition of immune cell activation via ITIM signaling (FcγRIIB); Modulation of antibody effector functions (e.g., ADCC, phagocytosis)