Quantitative and functional analysis of IgG Fc receptor molecules in polymorphonuclear leukocytes and monocyte macrophages in patients with essential mixed cryoglobulinaemia.

In order to gain insight into the role of IgG Fc receptors in essential mixed cryoglobulinaemia (EMC), we analyzed quantitatively the expression of such molecules on polymorphonuclear leukocytes (PMN) and assessed them, functionally, on PMN, tissue macrophages and circulating monocytes in 6 HLA-B8-, DR3-negative patients with EMC and glomerulonephritis. The Fc receptors expressed on PMN surface, as estimated by using AB 8.28 monoclonal antibody to PMN Fc receptor and 125I-labelled rabbit F(ab')2 fragments to mouse IgG as detecting system, were found to be quantitatively normal in EMC patients, whereas PMN Fc- receptor-mediated phagocytosis was reduced. Moreover, the patients were found to have prolonged macrophage clearance of IgG-sensitized autologous erythrocytes and reduced kinetics of ingestion of IgG-coated material by circulating monocytes. This impairment of Fc receptor function may play a remarkable role in the tissue localization of immune material in this disease.