The association between IFN-γ and IL-4 genetic polymorphisms and childhood susceptibility to bronchial asthma

The present study aims to investigate the association between the genetic polymorphisms of interferon (IFN)-gamma and interleukin (IL)-4 with childhood susceptibility to asthma and the levels of IFN-gamma, IL-4, and immunoglobulin (Ig) E among asthmatic children. A total of 100 asthmatic children and 122 control children were enrolled in the present study. The genotypes of the IFN-gamma gene at the -179G/T locus and the IL-4 gene at the -33C/T and -589C/T loci were detected using polymerase chain reaction with restriction fragment length polymorphism. The IFN-gamma gene at the +874A/T locus and the IFN-gamma CA repeats were tested using allele-specific and capillary electrophoresis, respectively, whereas the IFN-gamma, IL-4, and total IgE levels were measured using enzyme-linked immunosorbent assays. The 100 asthmatic children and the 122 control children were all GG homozygous in the 179 locus of the IFN-gamma gene, which shows that the IFN-y gene is not mutated at the 179 locus. No significant differences were found in terms of genotypic and allelic frequency distribution in the IFN-y gene or the CA repeat at the +874A/T locus between the asthmatic children and the control (P>0.05). An association was found between the polymorphism of the IFN-gamma gene at +874A/T and IFN-y levels. IFN-gamma expression was lower among patients with the AA genotype than those with the AT genotype (P<0.05); the genotypic and allelic frequency distributions of the IL-4 gene at -33C/T and -589C/T were significantly different between the asthmatic children and the control (P<0.05). The levels of IL-4 and IgE among children with TT genotype at the 33 and 589 loci were higher than those with the CT genotype, but only the polymorphism at -33C/T was associated with IL-4 levels (P<0.05). The polymorphisms of the IFN-gamma gene at +874A/T or the CA repeats are not correlated with susceptibility to asthma. Thus, the polymorphism at +874A/T is correlated with IFN-gamma level. The TT genotypes of the IL-4 gene at the 33 and -589 loci are associated with asthma susceptibility in children, and polymorphism at the 33 locus may be associated with IL-4 level. (C) 2011 Elsevier B.V. All rights reserved.