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 (Fc?RI). After binding IgG, CD64 interacts with an accessory chain known as the common ? chain (? chain), which possesses an ITAM motif that is necessary for triggering cellular activation. CD64 is constitutively found on only macrophages and monocytes, but trea™ent of polymorphonuclear leukocytes with cytokines like IFN? and G-CSF can induce CD64 expression on these cells.