Figure 1: Pathologic role of IL-6 in development of rheumatoid arthritis. Rheumatoid arthritis (RA) is a chronic inflammatory disease, characterized by immunological abnormalities, and systemic and joint inflammation. IL-6 performs a key function in the development of these characteristics. In the priming phase, IL-6 contributes to the imbalance between Th17 and Treg and the production of autoantibodies such as RF and ACPA. IL-6 also generates systemic inflammatory symptoms, signs and findings, and persistent joint inflammation through acting on multiple cells.