IgG Fc receptor (Fc γ R) is a member of the Ig superfamily, which plays a role in activating or inhibiting immune response. Human Fc γ Rs is identified as three subtypes: RI (CD64), RII (CD32) and RIII (CD16). There are three human Fc γ RII / CD32 genes (A, B and C), two crab eating monkeys (An and B), and one Fc γ RII B in mice. Fc γ RIIA of cynomolgus monkey consists of extracellular domain, transmembrane domain and cytoplasmic domain. The extracellular domain includes two IgG domains. The Fc γ RIIA protein of crab-eating monkey has 89% homology with human Fc γ RIIA. CD32a is expressed in a variety of immune cells such as macrophages, neutrophils and platelets. When it binds to ligands, it initiates inflammatory responses, including cytolysis, phagocytosis, degranulation and production of cytokines. This response can be regulated by co-expression of inhibitory receptors such as CD32B.