Promoter polymorphism of the IL‐18 gene is associated with atopic asthma in Tunisian children

Summary Several lines of evidence point to a relevant role of IL‐18 in the process of asthma. Some studies suggest that the polymorphism in the gene of IL‐18 can be involved in many inflammatory and atopic diseases such as asthma. The aim of our study is to estimate the frequency of the IL‐18‐ 607 C/A (rs 1946518) promoter polymorphism in Tunisian children with asthma. We investigated whether the presence of this polymorphism ‐607 C/A was associated with asthma or atopy and whether this polymorphism influenced the severity of asthma in affected children. We examined also the relationship between the IL‐18 gene polymorphism and the serum total IgE level. The IL‐18 /‐607 C/A polymorphism was analysed by polymerase chain reaction and restriction fragment‐length polymorphism (PCR‐RFLP) analysis. A total of 105 asthma patients and 112 controls as part of the whole children population were studied in a case‐control study. Among the 105 children with asthma, 40 were also studied for linkage analyses with their respective parents. We noted that the A allele was associated with statistically significant increases in the risk of asthma in the case‐control study (odd ratio (OR) = 1.55, 95% confidence interval (CI) 1.03–2.33. Moreover, the A allele was also associated with atopic asthma ( P  = 0.008), but not with asthma severity. The transmission disequilibrium test (TDT) analysis in this family study did not suggest a preferential transmission of the IL‐18 / ‐607 C/A polymorphism to affected children. There is no correlation between the IgE level and the IL‐18 ‐ 607 C/A promoter polymorphism. Our data indicate that IL‐18 ‐ 607 C/A promoter polymorphism is associated with susceptibility to developing asthma in Tunisian population.