The involvement of cytokines and chemokines in the pathogenesis of rheumatoid arthritis (RA) is well studied; however, the genetic bases behind this is not well understood. The aim of this study was to examine whether -572 G/C polymorphism in the IL-6 gene and 2767 A/G polymorphism in the 3'-untranslated region (UTR) of the IL-8 gene are associated with rheumatoid arthritis (RA).
We enrolled 199 RA patients and 130 normal controls. Polymerase chain reaction was used to identify the IL-6 -572G/C and IL-8 3'-UTR 2767A/G polymorphisms. The relationships between clinical manifestations of RA and the polymorphisms of each gene were investigated by comparing the genotypes among RA patients with different clinical variables.
We found no significant difference in the genotypic and allelic frequencies of the single nucleotide polymorphisms of IL-6 and IL-8 genes between RA patients and controls. Clinical characteristics such as age at onset, rheumatoid factor positivity, joint erosion and extra-articular manifestations were compared among patients with different genotypes of the IL-6 and IL-8 genes. We found that patients with IL-8 3'-UTR 2767AA genotype had a significantly younger age of onset of RA than patients without that genotype.
The IL-6 -572 G/C and IL-8 3'-UTR 2767A/G polymorphisms are not associated with the risk of developing rheumatoid arthritis. However, the finding that patients with IL-8 3'-UTR 2767AA developed RA at a younger age suggests that this genotype may influence the etiopathology of RA in patients in Taiwan. Therefore, further single nucleotide polymorphism studies of this 3'UTR region may give more novel findings and understanding of the genetic basis of rheumatoid arthritis.