Associations between circulating interleukin-17 levels and Behçet's disease and between IL-17 gene polymorphisms and disease susceptibility: a meta-analysis

Objective To systematically investigate the relationship between circulating interleukin-17 (IL-17) levels and Behçet's disease (BD) and the associations between polymorphisms in IL17 genes and BD susceptibility. Method We searched the Medline, Embase, and Cochrane databases for relevant articles. We performed a meta-analysis of serum/plasma IL-17 levels in BD patients and controls and evaluated the associations between IL17A rs4711998, rs8193036, and rs2275913 and IL17F rs763780 and rs2397084 polymorphisms and the risk of BD. Results Twelve studies, involving 901 patients with BD and 1,131 controls, were included. Our meta-analysis revealed that circulating IL-17 levels were significantly higher in the BD group than in the control group (SMD=1.422, 95% confidence interval [CI]=0.689-2.155, p<0.001). Subgroup analysis by data type indicated higher IL-17 levels in the BD group in both the original and calculated data populations. Stratification by publication year revealed significantly lower vitamin D levels in the SSc group in both recent and older publication years. No significant differences in IL-17 levels were observed between the active and inactive disease groups. We found no evidence of associations between BD and IL17A rs2275913, L17F rs763780, or rs2397084 polymorphisms. However, a significant association was found between BD and IL17A rs4711998 and rs8193036 polymorphisms in the pooled cohort of affected individuals compared to that in pooled controls (odds ratio [OR]=1.347, 95% CI=1.043-1.741, p<0.001; OR=0.691, 95% CI=0.542-0.880, p=0.003). Conclusion This meta-analysis revealed significantly higher circulating IL-17 levels in BD patients and showed evidence of associations between IL17A rs4711998 and rs8193036 polymorphisms and BD.