High affinity immunoglobulin gamma Fc receptor I (FcγRIa) (FcγRIa)

High affinity immunoglobulin gamma Fc receptor I (FcγRIa), also known as CD64, is a 72 kDa transmembrane glycoprotein that belongs to the immunoglobulin superfamily (UniProt: P12314). It is the only Fc receptor for IgG that exhibits high affinity for monomeric IgG1 and IgG3, allowing it to bind antibodies even at low concentrations (NCBI Gene: 2209). Primarily expressed on monocytes, macrophages, and interferon-gamma-activated neutrophils, FcγRIa plays a crucial role in the immune system by mediating phagocytosis, respiratory burst, and antibody-dependent cellular cytotoxicity (ADCC) (PubMed: 15276183). In clinical practice, the expression of CD64 on neutrophils is a highly specific and sensitive biomarker for systemic infection and sepsis (StatPearls: Sepsis). Therapeutically, FcγRIa is targeted by bispecific antibodies and immunotoxins to treat malignancies and chronic inflammatory conditions, leveraging its ability to trigger potent effector functions (Journal of Immunology: CD64 targeting).

Other names

CD64FCGR1AFc-gamma RIIGFR1Fc-gamma RIa

Binds the Fc region of monomeric IgG1 and IgG3 with high affinity, triggering signal transduction via the associated common gamma chain's immunoreceptor tyrosine-based activation motifs (ITAMs) (UniProt: P12314).