Objective: To investigate the correlation of - 1112C/T polymorphism of Interleukin-13 (IL-13) gene promoter with asthma and its effect on total plasma IgE levels.
Methods: One hundred asthmatic patients (the asthma group) and 100 healthy controls (the control group) were recruited. Polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) techniques were used to determine the - 1112 locus polymorphism, and the total plasma IgE levels were determined by ELISA.
Results: There were significant differences in C and T allele frequencies at -1112 locus (chi2 =9.01, P< 0.01), and in the genotype distribution such as CC, CT and TT between the two groups [chi2 =7.19, P < 0.05; OR(TT/CC) =2.99, 95%CI=1.06-8.41 (P<0.05); OR (CT/CC) =2.04, 95%CI=1.09-3.81 (P <0.05); OR(TT/CT) =1.46, 95% CI =0.49-4.37, P >0.05]. Allele T was associated with asthma, OR(T/C) = 2. 03, 95% CI =1.27-3.23 (P <0. 01). In the asthma group, the total plasma IgE levels of the patients with CC, CT and TT genotypes were (204 +/- 89)kU/L, (320 +/- 108)kU/L and (376 +/- 147) kU/L, respectively. While in the control group, the total plasma IgE levels of the subjects with CC, CT and TT genotypes were (96 +/- 34) kU/L, (122 +/- 42) kU/L and (150 +/- 36) kU/L, respectively. In both groups, the total plasma IgE levels in allele T carriers were higher than those in non- allele T carriers, and the total plasma IgE levels in the asthma group were higher than those in the control group with the same genotype.
Conclusions: The - 1112 locus polymorphism of IL-13 gene promoter may be an important candidate gene for asthma Allele T is associated with asthma and increases the total plasma IgE level via enhanced (enhancing) IL-13 gene expression.