P08637, O75015

CD16 is a crucial immune receptor that exists in two primary isoforms: CD16A (FcγRIIIA), a transmembrane protein expressed on natural killer (NK) cells and macrophages, and CD16B (FcγRIIIB), a glycosylphosphatidylinositol (GPI)-anchored protein found on neutrophils. The distinct structural configurations of these isoforms are essential for their specific roles in the immune response, with CD16A requiring association with the γ subunit of FcεRI or the ζ subunit of the TCR-CD3 complex for proper cell surface expression. This structural versatility allows CD16 to mediate antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis by binding the Fc region of IgG antibodies, thereby targeting and eliminating pathogens or infected cells effectively. CD16′s ability to exist both as a transmembrane and a GPI-anchored receptor highlights versatile functions in immune regulation and response.