Fc gamma receptor Ia (FCGR1A)

Fc gamma receptor Ia (FCGR1A, commonly known as CD64) is a high-affinity receptor for the Fc region of immunoglobulin G (IgG) and is primarily expressed on monocytes, macrophages, and dendritic cells, with inducible expression on neutrophils in response to inflammatory signals. This transmembrane glycoprotein (part of the immunoglobulin superfamily) bridges the adaptive immune response (antibody formation) to innate effector functions: it binds IgG-containing immune complexes and triggers cell activation pathways that drive phagocytosis, cytokine secretion, antibody-dependent cellular cytotoxicity, and antigen presentation. FCGR1A has important diagnostic and therapeutic implications in infectious diseases, leukemia subtypes (notably acute myeloid leukemia M4/M5), inflammation, and autoimmunity. Variants in the FCGR1A gene influence CD64 expression and have been linked to risk and severity in diseases such as sarcoidosis. FCGR1A's role in mediating the therapeutic efficacy of monoclonal antibodies (e.g., anti-CD20 in B-cell depletion) underscores its centrality in immunotherapy. Elevated CD64 levels on neutrophils serve as a biomarker for infection and immune activation, but therapeutic manipulation can pose safety risks due to excessive immune activation.

Other names

CD64FcγRIAFCGR1FCG1IGFR1CD64AFc-gamma RIFc-gamma RIAIgG Fc receptor I

Binding of IgG and immune complexes to FCGR1A activates phagocytosis, ADCC, cytokine release; Signal transduction via cytoplasmic domain modifies immune cell function.