| Objective:We aimed to investigate the serum level of interleukin-35 (IL-35), one of the Interleukin-12 (IL-12) family cytokines, in patients with rheumatoid arthritis (RA). The relationship between IL-35 and interleukin-17 (IL-17), immunological index markers and disease activity score were also studied, IL-17 is also an inflammatory cytokine closely related to the onset and joint destruction of RA, The possible roles IL-35 may play in the pathogenesis of RA were also discussedMethods:serum samples of newly diagnosed RA patients without any drug therapy and relapsed RA patients without glucocorticoid treatment were collected in the study. Thirty healthy volunteers were recruited as the control, serum samples were collected. ESR, CRP, anti-CCP, RF, tender joint count,swollen joint count, Ritchie articular index and DAS score of the patients were measured and recorded. All of RA patients (44 cases) were divided into three groups According to the DAS scores:(1) patients with DAS scores≤2.4 as low-grade disease activity; (2) patients with 2.43.7 as high-grade disease activity. Because of the limited number of patients with low-grade disease activity, we combined low-grade and medium-grade groups into low-medium grade disease activity group (33 cases). IL-35 and IL-17 had been detected in all 74 cases via ELISA. We analyzed the difference of the serum IL-35 and IL-17 levels between RA and control group and the high-grade disease activity group and low-medium grade disease activity group. The correlation between the serum levels of IL-35 and IL-17, ESR, CRP, anti-CCP, tender joint count, swollen joint count, Ritchie articular index, DAS scores in RA were also analyzed.Result:The IL-35 serum levels in different groups were as follows:RA group 34.0±9.7 ng/L, the high-grade disease activity group 30.4±10.1 ng/L, low-medium grade disease activity group 35.4±9.4 ng/L, health control group 63.4±14.8 ng/L. The serum IL-17 level in different groups were as follows: RA group 24.6±8.2 ng/L, control group 17.6±6.4 ng/L. The serum IL-35 level in RA group was lower than that in health group, and this difference reached statistical significance (p<0.05); the serum IL-35 level of high grade disease activity group was lower than that of low-medium grade disease activity group, but this difference did not reach statistical significance (p=0.141). serum IL-17 level in RA group was higher than that in health group, and this difference reached statistical significance (p<0.05); the serum levels of IL-35 in RA patient negatively correlated with IL-17 (r=-0.324,p=0.035),tender joint count(r=-0.509, p=0.001),swollen joint count (r=-0.373, p=0.001) and Ritchie articular index, it had reached statistical significance (p=0.14). Although serum IL-35 level also negatively correlated with DAS scores (r=-0.25, p=0.102) and RF (r=-0.015, p=0.925) positively correlated with ESR (r=0.022,p=0.887), CRP (r=0.135, p=0.383), anti-CCP (r=0.143,p=0.353), but it had not reached to level of statistic significance.Conclusion:The serum IL-35 levels in RA patients are lower than those in healthy controls and it negatively correlated with serum IL-17 levels,tender joint count,swollen joint count and Ritchie articular index. No statistic significantly corrections with ESR, CRP, anti-CCP, RF, and DAS scores are detected. There is no difference of the serum IL-35 level when comparing high-grade disease activity RA group with the low-medium grade disease activity RA group. IL-35 may participate in the pathogenesis of the loss of autoimmune tolerance and over activating process of the autoimmune T cells in RA. IL-35 therefore may be a new therapeutic target for RA patients.
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