Circulating levels of interleukin 1 beta and of interleukin 1 receptor antagonist in systemic juvenile chronic arthritis.

To measure circulating interleukin 1 beta (IL-1 beta) and IL-1 receptor antagonist (IL-1Ra) levels in patients with systemic juvenile chronic arthritis (JCA) and to evaluate their correlation with disease activity.IL-1 beta and IL-1Ra levels were measured by ELISA in 45 patients with JCA (20 systemic, 10 polyarticular and 15 pauciarticular) and in 15 healthy controls.Plasma IL-1 beta levels were undetectable in the majority of patients with systemic JCA, and detectable levels were not associated with different treatments or with parameters of disease severity. Serum IL-1Ra levels were markedly increased in patients with systemic JCA and significantly correlated with the persistence of systemic features, the extent and severity of joint involvement, and with C-reactive protein concentrations. Serum IL-1Ra levels were also significantly correlated with IL-6 levels.These results argue against a relevant role of IL-1 in systemic JCA. The increase in IL-1Ra levels does not appear to reflect an increase in IL-1 production, but may rather be induced by IL-6.