To identify possible imbalance of tumour necrosis factor alpha (TNFalpha) and its soluble receptors in the different subgroups of juvenile chronic arthritis (JCA).
Serum and synovial fluid samples from 45 children were examined, 25 pauciarticular JCA, 13 polyarticular JCA and seven spondyloarthropathy. TNFalpha, sTNFRI and sTNFRII levels were measured by EASIA and enzyme-linked immunosorbent assay (ELISA). Analysis of the results was carried out using non-parametric tests: Kruskal-Wallis one-way analysis of variance was used to compare the three clinical subgroups; the Mann-Whitney U-test was used to compare group medians.
Thirty-three serum samples were assayed for TNFalpha. There was no significant difference between the three groups using the Kruskal-Wallis analysis of variance. Analysis of synovial fluid TNF levels showed significantly lower levels in the spondyloarthropathy group compared with the pauciarticular JCA (P = 0.01) and the polyarticular group (P = 0.002). Significantly higher levels of sTNFRI were observed in the synovial fluid of the polyarticular JCA group compared with the pauciarticular JCA group (P = 0.004) and similarly for sTNFRII (P = 0.03). Molar ratios were calculated for TNF vs sTNFRI. The sTNFRI/TNFalpha ratio was significantly higher in the spondyloarthropathy group compared with the pauci- (P 0.003) and the polyarticular JCA subgroups (P = 0.003). The combined soluble receptor levels expressed as molar ratio to TNF again showed a significantly higher ratio in the spondyloarthropathy group compared with the pauciarticular group (P = 0.01) and compared with the polyarticular group (P = 0.05).
These results suggest that the increased joint destruction observed in polyarticular disease compared with the other two subtypes may be related to the lower sTNFR/TNFalpha ratios observed.