CD16 is a 50-65 kDa cell surface molecule that exists in two isoforms: a transmembrane form expressed by natural killer (NK) cells, and a glycosylphosphatidylinositol (GPI)-anchored form expressed by granulocytes. It serves as a low-affinity receptor for IgG (FcγRIII) and is a critical mediator of antibody-dependent cellular cytotoxicity (ADCC) by NK cells.
CD32 (Fcgr2) is a 40 kD transmembrane glycoprotein, member of the immunoglobulin superfamily. The extracellular region of CD32 consists of two Ig C-type domains that binds the Fc region from monomeric IgG with low affinity, but binds immune complexes efficiently. CD32 can mediate phagocytosis of immune complexes and modulate cell activation. CD32 is expressed by Macrophages, neutrophils, mast cells and B cells.
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