IL1B and rheumatoid arthritis: This response was also studied in HSF treated with IL-1β, a cytokine involved in the pathogenesis of chronic and severe arthritis/arthralgia following alphaviral infection [24,25] and well-characterized to induce the expression of pro-inflammatory mediators, such as CXCL8, IL-6 and COX2, in synovial fibroblasts from patients with rheumatoid arthritis [26,27].