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CD64 (Cluster of Differentiation 64) is a type of integral membrane glycoprotein known as an Fc receptor that binds monomeric IgG-type antibodies with high affinity. 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.

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.

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.

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. These three genes produce six different mRNA transcripts; two from CD64A, three from CD64B, and one from CD64C; by alternate splicing.

References

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. doi:10.1016/S0161-5890(98)00069-8. PMID 9881694.
2. Nimmerjahn F, Ravetch J (2006). "Fcgamma receptors: old friends and new family members". Immunity. 24 (1): 19–28. doi:10.1016/j.immuni.2005.11.010. 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. doi:10.1016/s0161-5890(98)00079-0. 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. doi:10.1084/jem.158.4.1092. PMC 2187379. 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. doi:10.1182/blood.V78.4.885.885. 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. doi:10.1016/S0021-9258(19)49591-4. PMID 1379234.

External links

• CD64+Antigens at the U.S. National Library of Medicine Medical Subject Headings (MeSH)

• Genes on human chromosome 1
• Clusters of differentiation
• Fc receptors