IL6 and rheumatoid arthritis: Although the pathogenesis of rheumatoid arthritis is poorly understood, inflammatory factors including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 as well as excessive proliferation of synovial cells [fibroblast-like synoviocytes (FLS)] are responsible for bone and cartilage erosions, playing a crucial role in development and progression of this disease (Aupperle et al., 1998; Roccaro et al., 2005).