Interleukin 6 gene polymorphism is associated with protein serum level and disease activity in Polish patients with rheumatoid arthritis.

Interleukin 6 (IL-6) is a pro-inflammatory cytokine involved in the development of rheumatoid arthritis (RA). The present study aimed to determine the possible association of the IL6 (rs1800795, G > C) polymorphism with RA susceptibility, disease progression and protein serum levels. Distribution of IL6 alleles and genotypes was similar in RA patients and controls. As expected, patients before induction of anti-tumour necrosis factor agents had significantly higher IL-6 levels as compared with controls (P = 0.002). The CC homozygous patients were characterised with the highest average concentrations of this pro-inflammatory cytokine before treatment (P = 0.028), and they also more frequently presented with more active disease (P = 0.048). These results imply that the IL6 rs1800795 CC homozygosity may play a rather unfavourable role in RA.