Association of the single‐nucleotide polymorphism and haplotype of the interleukin 18 gene with atopic dermatitis in Koreans

Abstract

Background IL‐18 is a proinflammatory cytokine that plays an important role for T‐helper type 1 (Th1) and Th2 cytokine in the presence/absence of IL‐12. It has been recently shown that human IL‐18 plays a role in atopic dermatitis (AD) by enhancing IL‐4 and IL‐13 production and by stimulating the synthesis of IgE. Objective We wanted to evaluate the associations of single‐nucleotide polymorphism (SNP) and the haplotype in the IL‐18 gene, hence we performed genotyping for the SNPs in the IL‐18 gene in AD patients and normal controls. Method We genotyped three SNPs from the IL‐18 gene for the 1120 case–control samples (646 AD patients and 474 normal controls). We measured the serum IL‐18, IL‐4 and IL‐13 concentrations in 74 individuals (25 ADe, 25 ADi and 24 controls) by performing ELISA. Result The rs795467 SNP and haplotype T–T–C were significantly associated with AD, and especially between the ADe and normal control groups (P=0.03 and 0.01). The serum IL‐18 concentration was higher in the AD group than in the normal controls without any correlation with the rs795467 polymorphism. We did not find any correlations between the serum IL‐18 levels and the SCORing atopic dermatitis index, the blood eosinophil counts and the ECP, and there was no correlation between the serum IL‐18 levels and the serum IL‐4 and IL‐13 levels. Conclusion We found that the one SNP and the haplotype T–T–C were strongly associated with the allergic type of AD, but not with the non‐allergic intrinsic type. These data support the hypothesis that IL‐18 up‐regulates IgE production, yet more experiments will be needed to prove the in vivo involvement of Th2 cytokine.