In patients with systemic lupus erythematosus (SLE)13–15, primary Sjögren’s syndrome (pSS)16,29, and psoriasis30, DNT that expands in peripheral blood and inflamed tissues are the major producers of the proinflammatory cytokine IL-17 and are believed to be pathogenic in these autoimmune diseases. Here, IL17A is linked to autoimmune disease.