IL‐5 and IL‐5 receptor alpha polymorphisms are associated with atopic dermatitis in Koreans

Background: Eosinophils are recruited into the affected tissue of asthma and atopic dermatitis (AD) patients. IL‐5 and IL‐5R are highly expressed in the AD skin lesions, yet the reported levels of IL‐8 are controversial. Method: We genotyped 17 singlenucleotide polymorphisms (SNPs) from five genes of the 1120 case‐control samples (646 AD and 474 controls). We measured the serum IL‐5 concentrations in 87 individuals [36 ADe (AD extrinsic), 18 ADi (AD intrinsic) and 33 controls] by ELISA, and compared the results among these groups. Result: The rs2522411SNP and haplotype T‐A in the IL‐5 gene were significantly associated with the ADe. The serum IL‐5 concentration was higher in the ADe than that in the ADi patients without any correlation with the rs2522411SNP. In the IL‐5RA gene, the rs334809SNP showed a weak association with AD, and the rs6771148SNP and the haplotype T‐C‐T of the three adjacent tagged SNPs had an effect on the blood eosinophil counts and the serum ECP levels in the AD patients. However, we could not detect any relationship between AD and the SNPs in the IL‐8 and IL‐8R genes. Conclusion: We found that the rs2522411SNP and the haplotype T‐A in the IL‐5 gene and the serum IL‐5 levels were strongly associated with the allergic type of AD, but not with the nonallergic type of AD. The association of the rs6771148SNP and the haplotype T‐C‐T in the IL5RA gene with the blood eosinophil counts and the serum ECP levels indicates that the IL5RA gene has a role for controlling eosinophils in the peripheral blood.