Some studies have shown that there are many IL-17 and Th17 cells in serum and synovial supernatant of inflammatory joints in patients with RA (Kirkham et al., 2006; Shen et al., 2009; Gullick et al., 2010; Leipe et al., 2010; Raychaudhuri et al., 2012; Gullick et al., 2013). The gene discussed is IL17A; the disease is rheumatoid arthritis.