IRF-1 gene variations influence IgE regulation and atopy.

Rationale The development of atopic diseases is characterized by skewed immune responses to common allergens. Only recently, interferons have been identified to play a crucial role in these mechanisms. Objectives: Because interferon regulatory factor (IRF)-1 is critical for interferon expression, we tested the hypotheses that genetic changes in this essential transcription factor may have consequences for the development of atopy. Methods: The IRF-1 gene locus was resequenced in 80 human chromosomes. Association and haplotype analyses were performed in a cross-sectional study population of German children from Dresden (n = 1,940), and results were replicated in a second population sample from Munich (n = 1,159), both part of the ISAAC (international Study of Asthma and Allergy in Childhood) phase It. Promoter polymorphism effects were studied using electrophoretic mobility shift assay and colorimetric binding assays. Allele-specific IRF-1 gene expression was studied in vitro using luciferase reporter assays, whereas we assessed ex vivo expression of IRF-1 by real-time polymerase chain reaction and IFN-gamma protein by Luminex technology (Bio-Rad, Hercules, CA). Statistical analyses were performed using SAS/Genetics (SAS 9.1.3; SAS Institute, Cary, NC). Measurements and Main Results: By resequencing, 49 polymorphisms were identified within the IRF-1 gene. Four blocks containing 11 polymorphisms were significantly associated with atopy, total IgE levels, or specific IgE levels in both populations (P < 0.05). Two polymorphisms changed transcription factor binding of nuclear factor (NF)-kappa B and EGR1 (early growth response 1) to the IRF-1 promoter, altered gene expression in vitro (P = 0.0004), and altered IRF-1 mRNA and IFN-gamma protein expression ex vivo. Conclusions: Our results suggest that functionally relevant IRF-1 polymorphisms influence atopy risk, potentially by altering transcription factor binding, IRF-1 gene expression, and IFN-gamma regulation.