MONOCYTE MACROPHAGE FC-GAMMA-RIII, UNLIKE FC-GAMMA-RIII ON NEUTROPHILS, IS NOT A PHOSPHATIDYLINOSITOL-LINKED PROTEIN

  • 15 June 1990
    • journal article
    • research article
    • Vol. 75  (12) , 2396-2400
Abstract
The low affinity IgG Fc receptor, Fc.gamma.RIII, expressed on circulating neutrophils, natural killer (NK) cells, and tissue macrophages, is involved in effector functions such as cytotoxicity and immune complex clearance by these cells. While Fc.gamma.RIII is reported to be aphosphatidylinositol (PI)-linked, rather than peptide-linked, protein on neutrophils and NK cells, its membrane linkage in macrophages has not been studied. We examined the sensitivity of Fc.gamma.RIII to cleavage by PI-specific phospholipase C (PI-PLC) in cultured monocytes and alveolar tissue macrophages and report that this receptor is not PI-linked on these cells. We also observed normal levels of Fc.gamma.RIII on cultured monocytes of a patient with paroxysmal nocturnal hemoglobinuria, a disease in which PI-linked proteins are deficient. The results suggest that Fc.gamma.RIII occurs solely in a transmembrane form in cells of the monocyte/macrophage lineage. In addition, we studied Fc.gamma.RIII on a cloned NK cell line and found it to be resistant to the effects of PI-PLC under conditions that cleaved Fc.gamma.RIII on neutrophils. Taken together, our results provide evidence for a distinct form of Fc.gamma.RIII that differs from the neutrophil receptor in its structure and, possibly, in its function.