Cytokines play an important role in mediating inflammation and in regulating the immune response of many rheumatological diseases. In patients with juvenile rheumatoid arthritis (JRA), levels of 6 cytokines, interleukin 1 alpha (IL-1 alpha), IL-1 beta (IL-1 beta), IL-2, IL-2 receptor (IL-2R), IL-6, and tumor necrosis factor alpha (TNF-alpha) were measured in serum and synovial fluid (SF) in an effort to evaluate their significance.
Serum concentrations of the 6 cytokines were measured in 62 patients with JRA including 22 pauciarticular onset, 26 polyarticular onset, and 14 systemic onset patients, and 29 disease and healthy controls using enzyme-linked immunoabsorbent assays (ELISA). Seventeen SF from patients with JRA were examined for cytokine levels.
Elevated serum levels of IL-2R were found in patients with systemic onset and elevated IL-2 levels in pauciarticular and polyarticular onset JRA as compared to controls. Pauciarticular and polyarticular onset patients also had elevated IL-1 alpha and IL-6 levels. There were no statistical differences found between the groups for TNF-alpha and IL-1 beta. SF revealed elevated levels of IL-1 beta, IL-2R, and IL-6; however, correlation was noted between serum and SF levels only for IL-1 alpha, not for the other cytokines. Mean serum levels of IL-2R in all onset types with active disease and IL-6 levels in active polyarticular and pauciarticular onset were elevated when compared with mean inactive levels.
Our studies indicate that (1) IL-1 alpha, IL-2, IL-2R, and IL-6 levels are increased in serum of patients with JRA with different onset types; (2) elevated levels of IL-1 beta, IL-2R, and IL-6 are found in their SF compared to serum levels; (3) a correlation exists between serum and SF levels only for IL-1 alpha; (4) mean IL-2R levels are elevated with active disease in all onset types and mean IL-6 levels with active polyarticular and pauciarticular onset disease are elevated compared to mean levels of inactive patients; and (5) cytokines may thus play a role as inflammatory mediators in JRA.