The Impact of Interleukin (IL)-33 Gene Polymorphisms and Environmental Factors on Risk of Asthma in the Iranian Population

Background Airway epithelial cells secrete Interleukin-33 in response to the different allergens. Several single nucleotide polymorphisms (SNP) of this cytokine have been reported to be involved in the development of asthma. We conducted this study to evaluate the impact of the two most common SNPs of the IL-33 gene (rs1342326 and rs3939286) and environmental factors on the susceptibility to asthma in the Iranian population. Subjects and Methods In this study, we enrolled 126 asthmatics patients and 300 age, sex-matched controls. Genotyping was performed by real-time PCR using the TaqMan SNP genotyping assay. Moreover, total serum IgE level, eosinophil count, and skin prick test were accomplished and complete history was taken from all the participants. Results The frequencies of mutant genotypes in both SNPs were significantly higher in asthmatics than controls. C/C genotype of rs1342326 [OR (95% CI) 2.50 (1.33-4.69)] and A/A genotype of rs3939286 [OR (95% CI) 2.18 (1.05-4.52)] were associated with higher risk of asthma development. While A/C+C/C genotype of rs1342326 was more prevalent in mild asthma [OR (95% CI) 2.36 (1.14-4.89)], G/A+A/A genotype of rs3939286 was associated with increased risk of moderate and severe asthma [OR (95% CI) 2.53 (1.30-4.94)]. Conclusion This study revealed that both IL-33 SNPs were associated with an increased risk of asthma. The rs1342326 was associated with atopic, mild and adult-onset asthma and a higher level of eosinophils in peripheral blood. However, rs3939286 was more frequent in moderate and severe asthma. Moreover, rs3939286 was associated with non-atopic and childhood-onset asthma.