Polymorphisms in toll-like receptor 4 are associated with severity but not susceptibility for asthma in a Chinese Han population

Background: Toll-like receptor 4 (TLR4) links human innate and adaptive immunity via bacterial endotoxin recognition, and has a considerable role in the pathogenesis of asthma. The effects of the genetic variants in TLR4 on asthma are still largely unknown. Aims and objectives: This study aimed to evaluate the effects of polymorphisms in TLR4 on asthma risk and asthma-related phenotypes in a Chinese Han population. Methods: We consecutively recruited 318 unrelated adult asthmatic patients and 352 healthy volunteers. Four tagging single nucleotide polymorphisms (SNPs) in TLR4 gene were detected using GenomeLab SNPstream or TaqMans Genotyping. We conducted case-control and case-only association studies between the selected tagging SNPs in TLR4 and asthma or asthma-related phenotypes. Results: We found no evidence to support a significant association between TLR4 SNPs and asthma susceptibility. However, our results revealed that the TT homozygote of rs1927914 was associated with lower FEV 1 % in asthmatic patients. An evidently positive association was found between the TT genotype of rs1927914, or the GG genotype of rs10983755 and rs1927907, and asthma severity ( P =0.024, 0.009, 0.013, respectively), which indicated that the C allele of rs1927914, and the A allele of rs10983755 and rs1927907 had a protective effect on asthma severity. Conclusion: TLR4 polymorphisms do not contribute to asthma susceptibility, but may influence the severity of asthma.