The importance of TLR5 signaling in the development of spontaneous gut inflammation has also been brought to light using the spontaneous C3H/HeJBir model of colitis as well as studies in IBD patients, which suggest a central role for TLR5 and bacterial flagellin, its natural ligand, in the pathogenesis of Crohn’s disease (CD), one of the major forms of IBD. The gene discussed is TLR5; the disease is Crohn disease.