Enhanced Fc receptor function of monocytes from patients with clinically active systemic lupus erythematosus: binding and degradation of soluble immune complexes in vitro.

Abstract

The in vitro Fc receptor function of monocytes as measured by using soluble immune complexes (IC) consisting of ovalbumin and 125I-labeled antibody to ovalbumin was examined in serum-free medium. Adherent monocytes were obtained from peripheral blood of 18 patients with systemic lupus erythematosus (SLE; 6 active, 12 inactive) and 13 normal controls. 5 X 10(5) monocytes were incubated with soluble IC containing 20 ng IgG for 16 hr at 4 degrees C, and for 4 hr and 16 hr at 37 degrees C, and then cell-associated and acid-soluble radioactivities were counted. After 16-hr incubation at 4 degrees C, there was no significant difference in the amount of cell-associated IC between monocytes from SLE patients and those from normal controls. After 4 hr incubation at 37 degrees C, monocytes from patients with active SLE bound and phagocytized more IC than those from patients with inactive SLE or from normal controls (P less than 0.01). After 16 hr incubation at 37 degrees C, degradation of soluble IC by monocytes from patients with active SLE greatly increased (P less than 0.003). These findings were discussed in relation to the possible pathophysiologic role of the mononuclear phagocyte system in SLE.