Abstract
OBJECTIVE: To determine whether levels of soluble tumor necrosis factor receptor 55 (sTNFR55), sTNFR75, and interleukin 1 receptor antagonist (IL-1Ra) can differentiate different subtypes of juvenile rheumatoid arthritis (JRA), and to determine if the levels of these proteins correlate with disease activity. METHODS: Serum sTNFR (55 and 75) and IL-1Ra levels were measured by ELISA in 34 patients with JRA and these values were correlated with disease subtype and activity. RESULTS: Serum sTNFR55 levels were significantly elevated in patients with systemic onset JRA (SoJRA) (mean +/- 2 SD, 2.9 +/- 1.8 ng/ml) (p < or = 0.05) compared to rheumatoid factor positive (RF+) polyarticular JRA (2.1 +/- 0.6), RF-polyarticular JRA (1.5 +/- 0.6), and pauciarticular JRA (1.4 +/- 0.4). There was a trend for elevation of sTNFR75 levels in patients with SoJRA compared to other subtypes (p = 0.08). More patients had elevated levels of sTNFR75 than sTNFR55 (15 vs 7). This was true for all subsets (SoJRA 7 vs 5; polyarticular JRA 4 vs 2; and pauciarticular JRA 4 vs 0). In contrast to sTNFR, IL-1Ra levels were significantly elevated in RF+ polyarticular JRA compared to the other subgroups (p < or = 0.001). We found statistically significant Pearson correlations between (1) sTNFR75 and hemoglobin concentration: and (2) IL-1Ra and number of active joints and number of joints with effusions. CONCLUSION: The increased serum level of sTNF receptors in SoJRA suggests that TNF is likely more important than IL-1 in systemic inflammation and in particular in SoJRA. Conversely, IL-1 is likely more important in the inflammatory arthritis of JRA and in particular in the pathogenesis of RF+ polyarticular JRA. Our results suggest that cytokines have differing roles in JRA subtypes and likely reflect JRA subtype heterogeneity.
