IL17A and rheumatoid arthritis: Moreover, synovial tissue of patients with RA is significantly enriched in IL-17 (84, 85), and IL-17 receptors were identified in the endothelial cells of RA synovium and chondrocytes derived from many types of arthritis, with the highest expression in osteoarthritis and SpA cartilages and the lowest in RA cartilage (82).