Asthma and IgE associated polymorphisms influence T H 17 pathway gene expression

Background: T H 17 cells participate in the pathogenesis of autoimmune and inflammatory diseases, such as asthma. Recently, our group identified associations of asthma and total serum IgE levels with single nucleotide polymorphisms (SNPs) in T H 17 pathway genes. We now investigated functional effects of these SNPs on gene expression within the T H 17 pathway in vitro . Methods: T H 17 pathway SNPs were genotyped (23 by MALDI-TOF MS; 2 by RFLP) in a randomly selected cohort (n=57, German adults). Expression of ten signature T H 17 pathway genes was measured by quantitative real-time PCR in peripheral blood mononuclear cells, stimulated with phytohemagglutinin, D. pteronyssinus , lipid A, or peptidoglycan. Induction of mRNA levels was compared between unstimulated and stimulated cells applying the delta-delta Ct method and correlated with genotypes. Measurements of T H 17 pathway cytokines were performed. Results: The RORyt SNP rs6693413, with minor allele frequency (MAF) 0.48, displayed allele-specific effects on IL17F mRNA induction in two of the tested stimulations (lowest p =0.013). Additionally, IL23A induction correlated with rs9395766 ( IL17A ; MAF=0.40) in all tested stimulations (lowest p =0.030). Conclusion: Our results demonstrate that certain SNPs in the T H 17 pathway are not only associated with asthma or IgE levels but also correlate with T H 17 pathway gene expression. The observed effects of RORyt and IL17A variants on IL17F and IL23A expression support previous genetic studies, which suggested a central role of the IL-23/IL-17 axis within T H 17 associated diseases.