Association of the interleukin-6 polymorphisms with systemic lupus erythematosus: a meta-analysis

Background Interleukin (IL)-6, an important proinflammatory cytokine, plays a potential pathological role in systemic lupus erythematosus (SLE). Studies on the relationship of IL-6 gene polymorphisms with SLE are inconclusive. The aim of this study was to estimate the relationship more precisely. Methods The databases of PubMed and Web of Science updated to 30 August 2014 were retrieved. Meta-analysis was conducted using allelic contrast, dominant, recessive and homozygote contrast models. Fifteen studies were included in this study and ethnicity-specific meta-analysis was performed on European, Iranian and Asian populations. Results Analysis for the IL-6-174 G/C polymorphism under all models except the homozygote contrast model indicated an association in the overall population (allelic contrast model: odds ratio (OR) 1.428, 95% confidence interval (CI) 1.124-1.812, dominant model: OR 1.382, 95% CI 1.037-1.842, recessive model: OR 1.610, 95% CI 1.158-2.240, homozygote contrast model: OR 1.759, 95% CI 0.989-3.127), as well as in European individuals under all four genetic models (allelic contrast model: OR 1.557, 95% CI 1.155-2.098, dominant model: OR 1.699, 95% CI 1.203-2.400, recessive model: OR 1.506, 95% CI 1.176-1.930, homozygote contrast model: OR 2.118, 95% CI 1.103-4.065). Analysis for the IL-6-572 G/C polymorphism indicated significant association in overall ethnicities under the recessive model (OR 1.491, 95% CI 1.104-2.014), but not under other models or in Asian individuals. In addition, significant association between the IL-6-174 G/C polymorphism and discoid skin lesions and antinuclear antibodies (ANAs) were found under the allelic contrast model and recessive model, respectively (discoid skin lesions: OR 2.271, 95% CI 1.053-4.895; ANAs: OR 2.244, 95% CI 1.141-4.416). Conclusion This meta-analysis provides evidence of the association between the IL-6 polymorphism and the risk of SLE, hinting that the IL-6-174 G/C and IL-6-572 G/C polymorphisms may play a role in SLE susceptibility.