Interleukin-21 gene polymorphism rs2221903 is associated with disease activity in patients with rheumatoid arthritis

INTRODUCTION: Interleukin-21 (IL-21) is a cytokine which plays a significant role in the pathogenesis and disease activity of rheumatoid arthritis (RA). Genetic polymorphisms in the IL-21 gene may alter the synthesis of IL-21. The aim of this study was to examine IL-21 and IL-21R polymorphisms in patients with RA. MATERIAL AND METHODS: We examined 422 patients with RA and 338 healthy controls. Single nucleotide polymorphisms (SNPs) within the IL-21 (rs6822844 G>T, rs6840978 C>T, rs2221903 T>C) and IL-21R (rs2285452 G>A) genes were genotyped using TaqMan genotyping assays. RESULTS: There were no statistically significant differences in the distribution of studied genotypes and alleles between RA patients and the control group. To examine whether IL-21 polymorphisms affect disease activity in RA patients, we compared the distribution of IL-21 genotypes between patients with DAS28 ≤ 2.5 (patients with remission of disease symptoms) and patients with DAS28 > 2.5 (patients with active RA). Among patients with DAS28 > 2.5, increased prevalence of rs2221903 CT and CC genotypes was observed (OR = 1.54; 95% CI: 1.04–2.28; p = 0.035). CONCLUSIONS: The results of this study suggest that IL-21 and IL-21R gene polymorphisms are not risk loci for RA susceptibility, whereas the IL-21 rs2221903 polymorphism is associated with disease activity.