FC-GAMMA-RIII (CD16) ON HUMAN MACROPHAGES IS A FUNCTIONAL PRODUCT OF THE FC-GAMMA-RIII-2 GENE

The low-affinity Fc receptor for immune-complexed IgG (Fc-gamma-RIII; CD 16) present on in vitro cultured human monocytes are encoded by an Fc-gamma-RIII-2 gene that, by cDNA sequence analysis, is identical to that expressed on tissue macrophages and on natural killer cells. In macrophages, Fc-gamma-RIII-2 encodes a glycoprotein of 52-62 kDa, with a peptide backbone of 33 kDa identical to that of the homologous receptor on natural killer cells. Like this and unlike in polymorphonuclear neutrophils, Fc-gamma-RIII (CD 16) on cultured monocytes is insensitive to phosphatidylinositol-specific phospholipase C, is not allelic for the neutrophil NA alloantigens NA-1/NA-2, is not recognized by a monoclonal antibody (1D3) detecting an epitope present only on neutrophil Fc-gamma-RIII (CD 16) and functions to trigger cytotoxicity upon ligand binding.