No association of IL-12p40 pro1.1 polymorphism with juvenile idiopathic arthritis.

BACKGROUND: IL-12p40 plays an important role in the activation of the T-cell lines like Th17 and Th1-cells. Theses cells are crucial in the pathogenesis of juvenile idiopathic arthritis. A polymorphism in its promoter region and the genotype IL12p40 pro1.1 leads to a higher production of IL-12p40. We studied whether there is a difference in the distribution of the genotype in patients with JIA and the healthy population. METHODS: In 883 patients and 321 healthy controls the IL-12p40 promoter genotype was identified by ARMS-PCR. RESULTS: There is no association of IL-12p40 pro polymorphism neither in patients with JIA compared to controls nor in subtypes of JIA compared to oligoarthritis. We found a non-significant tendency of a higher prevalence of the genotype pro1.1 in systemic arthritis (32.4%) and in rheumatoid factor negative polyarthritis (30.5%) and a lower pro1.1 genotype in persistent oligoarthritis (20.7%) and in enthesitis-related arthritis (17%). Likelihood of the occurrence of genotype IL12-p40 pro1.1 in patients with systemic arthritis (OR 1.722, CI 95% 1.344-2.615, p 0.0129) and RF-negative polyarthritis (OR 1.576, CI 95% 1.046-2.376, p 0.0367) compared to persistent oligoarthritis was significantly higher. This was also true for comparison of their homozygous genotypes IL-12p40 pro 1.1 and 2.2 in systemic arthritis (OR 1.779, CI 95 % 1.045-3.029, p 0.0338). However, in Bonferroni correction for multiple hypothesis this was not significant. CONCLUSION: A tendency of a higher prevalence of the genotype IL-12p40 pro1.1 in systemic arthritis and in rheumatoid factor negative polyarthritis was observed but not significant. Further investigations should be done to clarify the role IL-12p40 in the different subtypes of JIA.

The p38-mediated rapid down-regulation of cell surface gp130 expression impairs interleukin-6 signaling in the synovial fluid of juvenile idiopathic arthritis patients.

OBJECTIVE: Interleukin-6 (IL-6) signaling plays an important proinflammatory role, but this role is restricted by regulatory mechanisms that, for example, reduce the cell surface availability of the signal-transducing chain of the IL-6 receptor, gp130. The aim of this study was to determine whether the inflammatory environment in arthritic joints has an impact on monocytic gp130 surface expression and the extent to which regulatory processes in the synovial fluid (SF) can be reproduced in an in vitro model. METHODS: Flow cytometry and live cell imaging were used to measure the cell surface expression and internalization of gp130. STAT-3 phosphorylation was monitored by flow cytometry and Western blotting. RESULTS: In patients with juvenile idiopathic arthritis (JIA), levels of cell surface gp130 expression in SF monocytes were reduced compared to those in peripheral blood (PB) monocytes. These reduced levels were reproduced when PB monocytes from healthy donors were stimulated with SF, and this reduction was dependent on p38 MAPK. The induction of p38 by IL-1ß in PB monocytes interfered with IL-6 signaling due to the reduced cell surface expression of gp130. CONCLUSION: These results suggest that p38-mediated proinflammatory stimuli induce the down-regulation of gp130 on monocytes and thus restrict gp130-mediated signal transduction. This regulatory mechanism could be of relevance to processes in the inflamed joints of patients with JIA.