Defective Fc receptor-mediated function of the mononuclear phagocyte system in lupus nephritis.

To determine whether patients with systemic lupus erythematosus and nephritis have more profound defects in mononuclear phagocyte system clearance than their counterparts without renal disease, we studed Fc receptor-mediated splenic clearance function in 32 patients. Clearance half-times were prolonged in patients with lupus erythematosus compared with those in normal controls (p less than 0.0001) and longer in patients with renal disease than in those without (p less than 0.025). Both renal (tau = 0.45, p less than 0.0002) and nonrenal (tau = 0.35, p less than 0.003) disease activity were significantly but independently associated with clearance half-times. When matched for nonrenal activity, patients with nephritis had greater clearance dysfunction than their counterparts without renal disease. Circulating immune complexes did not correlate with clearance for all patients. Neither B8 nor DR3 histocompatibility antigen markers differentiated the renal and nonrenal disease subgroups. The greater Fc receptor-mediated clearance dysfunction, which occurs in patients with lupus erythematosus and nephritis, could lead to enhanced glomerular deposition of immune complexes as a primary event, or as a secondary event amplifying previously established lesions.