title: Association between interleukin-17a gene polymorphisms and asthma risk: a meta-analysis.
abstract: 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.
authors.affiliation: Department of Respiratory and Critical Care Medicine, West China Hospital of Sichuan University, Chengdu, Sichuan, China.
authors.forename: Min
authors.initials: M
authors.lastname: Zhu
authors.forename: Ting
authors.initials: T
authors.lastname: Wang
authors.forename: Renzhi
authors.initials: R
authors.lastname: Chen
authors.forename: Chengdi
authors.initials: C
authors.lastname: Wang
authors.forename: Shouzhi
authors.initials: S
authors.lastname: Liu
authors.forename: Yulin
authors.initials: Y
authors.lastname: Ji
mesh_terms: D000367:Age Factors; D044466:Asian People / Q000235:genetics; D001249:Asthma / Q000175:diagnosis / Q000208:ethnology / Q000235:genetics*; D016022:Case-Control Studies; D005787:Gene Frequency; D056726:Genetic Association Studies; D020022:Genetic Predisposition to Disease; D006801:Humans; D020381:Interleukin-17 / Q000235:genetics*; D016017:Odds Ratio; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D065840:Protective Factors; D018570:Risk Assessment; D012307:Risk Factors
chemical_list: C508717:IL17A protein, human; D020381:Interleukin-17