Background: The acute skin lesions of atopic dermatitis (AD) are associated with Th2 cells; however, the chronic skin lesions of AD are associated with Th1 cells via the action of IL-12.
Objective: We evaluated the associations of single nucleotide polymorphisms (SNPs) and haplotype in the IL-12 and IL-12 receptor genes, and determined the gene-gene interactions between the SNPs of these genes and the SNPs of the IL-18 gene that we previously reported.
Method: We genotyped 24 SNPs from 4 IL-12/IL-12R genes for 1089 case-control samples (631 AD patients and 458 normal controls). We measured the serum IL-12 concentrations in 89 individuals (79 AD patients and 10 controls) by ELISA. We analyzed the SNPs and haplotypes in each gene and also searched for the gene-gene interactions.
Result: The rs582504 (IVS-798A/T) SNP and the haplotype TA (rs582054 and rs2243151) in the IL-12A gene, and the rs438421 (IVS12+1266T/C) SNP and the haplotype CCA (rs375947, rs438421, and rs1870063) in the IL-12RB1 gene were significantly associated with the AD phenotype. We showed that the rs438421 polymorphism in the IL-12RB1 (TT) gene and the rs2066446 polymorphism in the IL-12RB2 (AA) gene had a significant interaction to develop the ADe phenotype (allergic type of AD), and those individuals with the risk alleles, TT/AA/CC (IL-12RB1/IL-12RB2/IL-18), have more than a 10-fold increased risk to develop ADe.
Conclusion: This study provides evidence for a significant interaction between the IL-12RB1 and IL-12RB2 genes that contribute to a 4-fold increased risk for developing ADe. In addition to the IL-12R interaction, we suggest that the IL-18 gene can significantly interact with the IL-12R gene to develop ADe. In addition to the interaction, the SNPs and haplotypes in the IL-12A and IL-12RB1 genes are independently and significantly associated with the AD phenotype, and especially with the ADe phenotype. This data may contribute to our understanding of AD genetic interactions and account for the additional risk of certain patients to develop AD.
2009 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.