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 monocytes from 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 monocytes from patients with active SLE was considerably higher than that in normal monocytes. Moreover, monocytes from patients with active SLE produced increased amounts of IL-1Ra in response to adherent IgG, compared with monocytes from 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.