CD16 is expressed on the surface of natural killer (NK) cells, neutrophil polymorphonuclear leukocytes, monocytes and macrophages. CD16 is one of the three subtypes of Fc- Immunoglobulin G (IgG) receptors . These receptors are distributed widely on many cells of the immune system and contribute to the pathogenesis of immune disorders. CD16 plays a role in signal transduction and NK cell activation.