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CD16, also known as FcγRIII, is a type of glycoprotein belonging to the immunoglobulin superfamily. It is divided into two subtypes: CD16a （FcγRIIIa） and CD16b （FcγRIIIb）. CD16a is a transmembrane protein mainly expressed on natural killer （NK） cells, monocytes, and some T cell subsets, while CD16b is a GPI-anchored protein primarily found on neutrophils. CD16a can mediate antibody-dependent cell cytotoxicity （ADCC） by binding to the Fc region of IgG antibodies, which is crucial for the immune system to eliminate virus-infected cells and cancer cells. Additionally, CD16a is one of the core markers for defining NK cells and can promote their proliferation and secretion of cytotoxic cytokines. In cancer immunotherapy, CD16a is an important target protein, and some monoclonal antibody drugs are designed to enhance its binding ability to boost immune responses.