OBJECTIVETo investigate the distribution characteristics of the single nucleotide polymorphisms (SNPs) in the promoter region of the toll-like receptor 9 gene (TLR9) in Chinese Han children from Zhejiang province, and their associations with asthma susceptibility and phenotypes.

METHODSA case-control study was conducted. A total of 312 asthmatic children aged between 1.9 and 11.6 and 339 age matched healthy controls were enrolled in this study from April 2007 to November 2008. The -1486 C/T in rs187084 and -1237 C/T in rs5743836 loci of the TLR9 gene were genotyped by direct DNA sequencing of the PCR products. Serum levels of IFN gamma, IL-12 and IL-4 were detected by enzyme linked immunosorbent assay.Serum levels of total IgE were detected by chemiluminescence, and serum levels of antigen specific IgE antibodies were detected by fluoroenzymeimmunoassay.

RESULTS(1) The -1486 C/T polymorphism was identified in both groups. The genotype frequencies of TT, TC and CC at -1486 C/T were 41.0%, 44.3%, 14.7% in the healthy controls, and 38.8%, 48.4%, 12.8% in the asthmatic children. The -1237 C/T polymorphism was not detected in the population. (2) There were no statistically significant differences in the allele and genotype frequencies at the -1486 C/T locus between the two groups (P;>0.05). (3) Serum levels of IFN gamma and IL-4 differed significantly among the three genotypes at the -1486 C/T locus in asthmatic children (P<0.01). The CC genotype had the lowest levels of serum IFN gamma and the highest levels of serum IL-4 among the three genotypes. There were no significant differences in these cytokines among the healthy controls (P>0.05). No statistical differences of serum IL-12 were found among the three genotypes in the two groups (P>0.05). (4) There were no significant differences of total IgE (log-transformed) among the three genotypes in the asthmatic children (P>0.05).

CONCLUSIONThe -1237 C/T polymorphism of TLR9 gene was not detected in Chinese Han children in this study. The -1486 C/T polymorphism was associated with the levels of serum IFN gamma and IL-4 in children with asthma. However, there were no correlations between the -1486C/T polymorphism and serum IL-12 levels, total IgE levels or asthmatic susceptibility.