Differences in synovial fluid cytokine levels between juvenile and adult rheumatoid arthritis

Objective. To evaluate quantitative or qualitative differences in synovial fluid (SF) cytokine levels among patients with systemic juvenile rheumatoid arthritis (JRA), antinuclear antibody positive pauciarticular JRA, or adult RA. Methods. SF levels of interleukin 1α (IL-1α), IL-1β, IL-I receptor antagonist (IL-1Ra) IL-11, tumor necrosis factor-α, (TNF-α), soluble TNF receptor 1 (sTNFRI), leukemia inhibitory factor (LIF), all measured by immunoassays, and of IL-6, measured with a bioassay using B9 cells, were evaluated in 11 patients with systemic JRA. 24 with pauciarticular JRA, and 22 adult patients with RA. Results. SF IL-6 levels were significantly higher in patients with systemic JRA than patients with pauciarticular JRA (p = 0.003) or RA (p = 0.002). IL-1α was detectable in 12/24 SF samples from pauciarticular JRA, in 2/22 SF from RA, and in no sample from systemic JRA (p = 0.004 vs RA; p = 0.005 vs systemic JRA). SF IL- 11 levels were significantly higher in patients with RA than patients with systemic JRA (p = 0.012) or pauciarticular JRA (p = 0.005). We found no significant differences in SF levels of IL-1β, IL-IRa, TNF-α, sTNFR1, or LIF. Conclusion. In systemic JRA, SF levels of IL-6 are significantly higher than in pauciarticular JRA or in RA: IL-1α is present in a significant proportion of patients with pauciarticular JRA, but not in those with RA or systemic JRA.