Polymorphisms of the IL-18 promoter and bronchial asthma.

To study the association of polymorphisms of the IL-18 promoter (-607C/A and -137G/C) with bronchial asthma, 120 subjects with bronchial asthma were selected as the experimental group (49 cases with bronchial asthma and allergic rhinitis as experimental group 1 and 71 cases with bronchial asthma without allergic rhinitis as experimental group 2) and 120 healthy individuals were selected as the control group. A polymerase chain reaction sequence-specific primer (PCR-SSP) was used to identify the genotypic polymorphisms between the experimental and control groups. The results revealed that the frequencies of the CC, CA and AA genotypes at -607C/A in experimental group 1 were 18.37, 40.82 and 40.82%, respectively; these frequencies were 32.39, 54.92 and 12.68%, respectively, in experimental group 2. There was a statistically significant difference in the genotype distribution between experimental groups 1 and 2 (χ²=12.81; P<0.05). The allele frequencies of genotypes C and A were 38.78 and 61.22%, respectively, in experimental group 1 and 59.86 and 40.14%, respectively, in experimental group 2. The allele frequencies at -607C/A were significantly different between experimental groups 1 and 2 (χ²=10.32; P<0.05). Frequencies of genotypes GG, GC and CC at -137C/A in experimental group 1 were 48.98, 46.94 and 4.08%, respectively, and 80.28, 14.08 and 4.08% in experimental group 2 with significant difference (χ²=15.73, P<0.05). Allele frequencies of G and C in experimental group 1 were 72.45 and 27.55%, and 87.32 and 12.68% in experimental group 2 with statistically significant difference (χ²=8.42, P<0.05). In conclusion, polymorphisms of the IL-18 gene promoter at -607C/A and -137G/C were associated with allergic rhinitis in bronchial asthma, indicating that polymorphisms of the IL-18 gene promoter at -607C/A and -137G/C differentially affect the pathogenesis of asthma and allergic rhinitis.