To investigate the single-nucleotide polymorphisms (SNPs) at positions -572 and -174 in the promoter region of interleukin-6 (IL-6) gene and at -607 and -137 in the promoter region of interleukin-18 (IL-18) gene for their association with rheumatoid arthritis (RA) in the Chinese Han population in Guangdong Province.
SNPs of IL-6 and IL-18 genes were detected in 120 patients with RA and 168 normal subjects using polymerase chain reaction with sequence-specific primers (PCR-SSP).
SNPs at -572 and -174 of IL-6 gene and at -607 and -137 of IL-18 gene were detected in this population. There was a significant difference in the genotype and allele frequency at -572 and -174 of IL-6 gene and -607 of IL-18 gene (P<0.001), but not in the distribution of genotype frequencies at -137 of IL-18 gene between the RA patients and healthy subjects (P=0.141). A significant difference was found, however, in the allele frequency at -137 of IL-18 (P=0.024). Logistic regression analysis revealed significant association of age, gender, IL-6 gene -572, -174 and IL-18 gene -137 SNPs with RA (P<0.05).
The polymorphisms of the promoter region of IL-6 gene at positions -572 and -174 is probably associated with RA, and further study is needed to understand the relation of the polymorphisms of IL-18 gene at positions -607C/A and-137G/C with RA.