CD64 (Cluster of Differentiation 64) is a type of
integral membrane glycoprotein
Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycos ...
known as an
Fc receptor that binds
monomeric IgG-type
antibodies
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
with high
affinity
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. It is more commonly known as Fc-gamma receptor 1 (FcγRI). After binding
IgG
Immunoglobulin G (Ig G) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG a ...
, 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
A signal peptide (sometimes referred to as signal sequence, targeting signal, localization signal, localization sequence, transit peptide, leader sequence or leader peptide) is a short peptide (usually 16-30 amino acids long) present at the N-ter ...
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 of the genes.
References
External links
*
{{Immune receptors
Clusters of differentiation
Fc receptors