IL17A and synovitis: RA is a chronic inflammatory disease, mainly synovitis, and is mainly characterized by inflammation of the joints and infiltration of innate and adaptive immune cells [18], with obvious proliferation of the inner lining layer and subsynovial layer, the proliferation of fibroblasts, the excessive production of pro-inflammatory mediators by macrophages and lymphocytes, such as TNFα, IFNγ, IL-1β, IL-6, IL-17, etc., can promote angiogenesis, lead to the formation of pannus and cause destruction of adjacent of cartilage and bone [19].