Association between interleukin-17a gene polymorphisms and asthma risk: a meta-analysis.

BACKGROUND Interleukin-17A (IL-17A), a proinflammatory cytokine, plays an important role in the pathogenesis of asthma. Considerable research has assessed the association between IL-17A polymorphisms and asthma risk, but the results are inconsistent. OBJECTIVE This meta-analysis was carried out to make a more precise estimation of the relationship between IL-17A polymorphisms and asthma risk. METHODS The PUBMED, MEDLINE, EMBASE, Chinese National Knowledge Infrastructure and Wan Fang databases were searched systemically on December 12, 2014 and data were extracted from eligible studies by two independent reviewers. Meta-analysis, sub-group analysis, sensitivity analysis and publication bias assessments were all done using Stata 12.1 software. RESULTS The IL-17A -737C/T polymorphism and IL-17A -197G/A polymorphism were included in the analysis with seven case-control studies. Asthma patients (n = 2882) and healthy controls (n = 2093) were included. The IL17A -737C/T polymorphism was found to have a significantly protective effect on asthma in the allele model (OR = 0.86, 95% CI 0.78-0.96, P = 0.007), dominant model (OR = 0.76, 95% CI 0.65-0.88, P <0.001) and heterozygous model (OR = 0.75, 95% CI 0.64-0.88, P < 0.001) in the overall analysis. Stratified by ethnicity and age, the effects were also significant in the Asian population and in children. However, for IL-17A -197G/A, no significant association was revealed either in the overall analysis in the ethnicity-special subgroup analysis. CONCLUSIONS The IL-17A -737C/T polymorphism is likely to contribute to protection against asthma, while the IL-17A -197G/A polymorphism may not be associated with asthma susceptibility.