Immune complex clearance by monocytes and macrophages in systemic lupus erythematosus

During the last 30 years more than 700 patients with systemic lupus erythematosus (SLE) have been treated in our department with their data analyzed. Here we focus on circulating immune complex (CIC) and its clearance. We demonstrated, microscopically, that the uptake of IgG sensitized erythrocytes (EA), via monocytes (Mo) of SLE patients, was elevated and correlated with the high CIC content. The in Vivo clearance of sensitized autolog E, and the in vitro degradation rate of soluble IC by Mo of SLE patients were decreased. This discrepancy could be explained by the molecular heterogeneity of FcgammaR being recognized lately. The high FcgammaRI expression and the low FcgammaRII and FcgammaRIII expression were detected by monoclonal antibodies (mAb) on Mo in SLE. The EA bound mostly to FcgammaRI, FcgammaRII and FcgammaRIII have a role in phagocytosis. The decreased receptor expression and function correlated with the disease activity and renal involvement. The shedding of receptors may cause a decrease on Mo surface, with the soluble FcRII and FcgammaRIII levels being elevated in serum of SLE patients. The mannose binding receptors, which play a role in the phagocytosis of apoptotic cells in SLE, were also decreased on Mo of SLE patients.