Systemic lupus erythematosus monocytes are less responsive to interleukin‐10 in the presence of immune complexes

Abstract

Objective Systemic lupus erythematosus (SLE) is a systemic inflammatory disease characterized by autoantibody production and immune complex deposition. The level of interleukin‐10 (IL‐10), predominantly an antiinflammatory cytokine, is paradoxically elevated in patients with SLE. The aim of this study was to examine the hypothesis that the antiinflammatory function of IL‐10 is impaired in monocytes from patients with SLE with long‐term exposure to immune complexes. Methods CD14+ monocytes were isolated from healthy donors and patients with SLE. Cultured CD14+ cells were treated with heat‐aggregated human IgG (325 μg/ml) in the presence or absence of IL‐10 (20 ng/ml). To study gene expression, RNA was extracted 3 hours after treatment. To study cytokine production, supernatants were harvested after 8 hours. To study IL‐10 signaling, cell lysates were obtained from CD14+ cells treated with human IgG (325 μg/ml) for 1 hour followed by IL‐10 (20 ng/ml) treatment for 10 minutes. Western blot analysis was used to assess STAT‐3 phosphorylation. All experiments were performed in pairs. Results When stimulated with human IgG, SLE monocytes produced more tumor necrosis factor α (TNFα) and IL‐6 than did control cells. The suppressive effect of IL‐10 on human IgG–induced TNFα and IL‐6 production was lower in SLE monocytes compared with control monocytes, although IL‐10 receptor expression was similar in SLE and control monocytes. Human IgG suppressed IL‐10 receptor expression and altered IL‐10 signaling in control monocytes. Like SLE monocytes, interferon‐α (IFNα)–primed control monocytes stimulated with human IgG were also less responsive to IL‐10. Conclusion Human IgG and IFNα modulate IL‐10 function. In SLE monocytes, which are considered to be IFNα primed and persistently exposed to immune complexes, responses to IL‐10 are abnormal, limiting the antiinflammatory effect of this cytokine.