R ecently, type I interferons IFN-α and IFN-β (IFN-α/β) have been evaluated in pilot clinical trials for the treatment of active ulcerative colitis. However, the underlying mechanisms that may contribute to a potential therapeutic effect are incompletely understood. A new study in this issue demonstrates a protective role for IFN-α/β, induced by activation of a Toll-like receptor 9–dependent pathway, in a rodent model of experimental colitis.