Study On Relationship Between Interleukin-18 Gene Polymorphisms And Susceptiblity To Pulmonary Tuberculosis

Background:Like other diseases,tuberculosis(TB) results from multiple conditions. TB beginning and severity are mediated by both environmental and genetic factors.In TB studies,important work is realization of the genetic background and identification of genetic factors resulting in TB development and phenomena.Interleukin-18(IL-18) is a multifunctional cytokine capable of inducing either Th1 or Th2 polarization depending on the immunologic milieu.Polymorphisms in the gene that encodes the IL-18 may influence the host response to Mycobacterium tuberculosis(M.tb) infection.Objective:This study attempts to evaluate the influence of these polymorphisms in the IL-18 gene in pulmonary TB patients and healthy controls.We investigated whether IL- 18 single nucleotide polymorphisms(SNPs) are involved Han population in China.Mehtods:94 pulmonary TB patients and 93 healthy controls were enrolled in this study.We sequenced IL-18 to detect polymorphisms and genotyped SNPs.Single nucleotide polymorphisms of the IL-18 gene were analyzed by SNaPshot.Statistical analyses of linkage disequilibrium(LD) and haplotypes single polymorphisms made use of SHEsis software.Results:Sequencing of IL-18 and chose three SNPs to be genotyped by SNaPshot in 94 TB cases and 93 healthy controls,including -607A/C,+105A/C,-372C/G.The SHEsis identified four haplotype blocks(ACA,ACC,AGA,CCA)for the markers genotyped in IL- 18 in the samples studied,their haplotype frequencies were distributed in the case group 1.1%,10.2%,36.0%,52.7%and in the control group 2.7%,10.6%,43.1%,43.6 %.There was strong LD between -607A/C and -372C/G and no statistically significant differences between cases and controls in allele,genotype,and haplotype frequencies of the three IL- 18 single nucleotide polymorphisms(SNPs) between TB patients and controls.Conclusions:IL-18 polymorphisms do not appear to influence the susceptibility to TB in tested population.We suggest that IL-18 gene polymorphisms may not major genetic factors for susceptibility to pulmonary tuberculosis in the populations investigated.