CD64

High affinity immunoglobulingamma Fc receptor I, also known as FCGR1 and CD64, is an integralmembrane glycoprotein and a member of the immunoglobulin superfamily. CD64is a high affinity receptor for the Fc region of IgG gamma and functions inboth innate and adaptive immune responses. Receptors that recognize the Fcportion of IgG function in the regulation of immune response and are dividedinto three classes designated CD64, CD32, and CD16. CD64 is structurallycomposed of a signal peptide that allows its transport to the surfaceof a cell, three extracellular immunoglobulin domains of theC2-type that it uses to bind antibody, a hydrophobic transmembrane domain,and a short cytoplasmic tail. CD64 is constitutively found on onlymacrophages and monocytes, but treatment of polymorphonuclearleukocytes with cytokines like IFNγ and G-CSF caninduce CD64 expression on these cells. The inactivation of the mouse CD64resulted in a wide range of defects in antibody Fc-dependent functions. MouseCD64 is an early participant in Fc-dependent cell activation and in thedevelopment of immune responses.