In the course of RA, fibroblast-like synoviocytes secrete a large number of pro-inflammatory factors such as TNF-α, IL-1β, IL-6, IL-8, IL-17A, and IL-23, which form a cytokine network to promote and maintain inflammation of the synovial membrane (McInnes and Liew, 2005). Here, IL17A is linked to rheumatoid arthritis.