Interleukin‐1 receptor antagonist in patients with active systemic lupus erythematosus: enhanced production by monocytes and correlation with disease activity

Objective. To evaluate the relationship between the serum concentration of interleukin-1 receptor antagonist(IL-1Ra) and systemic lupus erythematosus (SLE) disease activity, and to investigate the expression of IL-1Ra messenger RNA (mRNA) and its production by monocytesfrom patients with SLE. Methods. Serum IL-1Ra was measured by enzyme-linked immunosorbent assay, and expression of IL-1Ra mRNA was determined by Northern blotting. Results. Serum IL-1Ra concentrations were significantly higher in patients with active SLE compared with normal subjects and patients with other rheumatic diseases, and showed a strong correlation with SLE disease activity. IL-1Ra mRNA expression in freshly isolated monocytesfrom patients with active SLE was considerably higher than that in normal monocytes. Moreover, monocytesfrom patients with active SLE produced increased amounts of IL-1Ra in response to adherent IgG, compared with monocytesfrom normal subjects. Conclusion. A high serum concentration of IL-1Ra is a pathophysiologic feature of active SLE and a good indicator of disease activity. Functional changes of monocytes, such as increased secretion of IL-1Ra in response to adherent IgG and enhanced expression of IL-1Ra mRNA in freshly isolated cells, may be involved in the enhanced IL-1Ra production in active SLE. High concentrations of IL-1Ra in the circulation and possibly in peripheral lymphoid tissues may influence immunologic and inflammatory features of SLE.