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CD64 is a type of integral membrane glycoprotein known as an Fc receptor that binds monomeric IgG-type antibodies with high affinity.^[1] It is more commonly known as Fc-gamma receptor 1 (FcγRI). After binding IgG, CD64 interacts with an accessory chain known as the common γ chain (γ chain), which possesses an ITAM motif that is necessary for triggering cellular activation.^[2]

Structurally CD64 is composed of a signal peptide that allows its transport to the surface of a cell, three extracellular immunoglobulin domains of the C2-type that it uses to bind antibody, a hydrophobic transmembrane domain, and a short cytoplasmic tail.^[3]

CD64 is constitutively found on only macrophages and monocytes, but treatment of polymorphonuclear leukocytes with cytokines like IFNγ and G-CSF can induce CD64 expression on these cells.^[4][5]

There are three distinct (but highly similar) genes in humans for CD64 called FcγRIA (CD64A), FcγRIB (CD64B), and FcγRIC (CD64C) that are located on chromosome 1.^[6] These three genes produce six different mRNA transcripts ; two from CD64A, three from CD64B, and one from CD64C; by alternate splicing of the genes.^[7]

1. ^ Hulett M, Hogarth P (1998). "The second and third extracellular domains of FcgammaRI (CD64) confer the unique high affinity binding of IgG2a". Mol Immunol 35 (14-15): 989-96. PMID 9881694. 
2. ^ Nimmerjahn F, Ravetch J (2006). "Fcgamma receptors: old friends and new family members". Immunity 24 (1): 19-28. PMID 16413920. 
3. ^ Ernst L, Duchemin A, Miller K, Anderson C (1998). "Molecular characterization of six variant Fcgamma receptor class I (CD64) transcripts". Mol Immunol 35 (14-15): 943-54. PMID 9881690. 
4. ^ Perussia B, Dayton E, Lazarus R, Fanning V, Trinchieri G (1983). "Immune interferon induces the receptor for monomeric IgG1 on human monocytic and myeloid cells". J Exp Med 158 (4): 1092-113. PMID 6225822. 
5. ^ Repp R, Valerius T, Sendler A, Gramatzki M, Iro H, Kalden J, Platzer E (1991). "Neutrophils express the high affinity receptor for IgG (Fc gamma RI, CD64) after in vivo application of recombinant human granulocyte colony-stimulating factor". Blood 78 (4): 885-9. PMID 1714327. 
6. ^ Ernst L, van de Winkel J, Chiu I, Anderson C (1992). "Three genes for the human high affinity Fc receptor for IgG (Fc gamma RI) encode four distinct transcription products". J Biol Chem 267 (22): 15692-700. PMID 1379234. 
7. ^ Ernst L, Duchemin A, Miller K, Anderson C (1998). "Molecular characterization of six variant Fcgamma receptor class I (CD64) transcripts". Mol Immunol 35 (14-15): 943-54. PMID 9881690. 

• MeSH CD64+Antigens

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