In contrast, anti-IL-12/23 (p40/p19) and anti-IL23p19 are efficacious against Crohn’s disease, whereas anti-IL-17 worsens the disease, suggesting a role for IL-23 in local inflammation in gut epithelial cells and a protective role for IL-17 in Crohn’s disease. The gene discussed is IL17A; the disease is Crohn disease.