Association of interferon-γ and interferon regulatory factor 1 polymorphisms with asthma in a family-based association study in Taiwan

BACKGROUND: Asthma is a multi-factorial disorder caused by complex interactions between genetic and environmental factors. IFN-gamma and IFN regulatory factor 1 (IRF-1) affect Th1/Th2 cytokine balance, and influence the differentiation of Th2 cells, which influence the development of asthma. OBJECTIVE: This study investigated CA repeats polymorphism of the IFN-gamma gene and GT repeats polymorphism of the IRF-1 gene, which may predispose individuals to asthma pathogenesis. METHODS: In the present study, we used the transmission/disequilibrium test (TDT) to investigate the relationship between asthma and the IFN-gamma and IRF-1 polymorphisms by studying 348 subjects composed of 232 parents and 116 asthmatic children. RESULTS: For global TDT test, IFN-gamma CA repeats and IRF-1 GT repeat polymorphisms showed a significant association with asthma in children (P=0.009 and 0.017, respectively). We demonstrated that 13 CA repeats (138 bp) of IFN-gamma gene and 11 GT repeats (306 bp) of IRF-1 gene are significantly preferentially transmitted to asthmatic children (T/NT=89/61, chi2=8.43, P<0.005 and T/NT=75/49, chi2=8.18, P<0.005, respectively). The offspring will have an increased risk of asthma when their parents transmit IFN-gamma 13 CA repeats (OR=1.83, P=0.009) and IRF1 11 GT repeats (OR=1.88, P=0.007) to them. But we observed that the IFN-gamma and IRF-1 polymorphisms are not associated with IgE concentrations. CONCLUSION: These findings provide strong evidence of which IFN-gamma CA repeat and IRF-1 GT repeat polymorphisms influence the risk of asthma for children in Taiwan.