TNFSF15 and Crohn ileitis: Consistent with human IBD, TL1A transgenic mice develop spontaneous ileitis and intestinal collagen deposition that is exaggerated under colitigenic conditions and results in severe inflammation and fibrosis17–19.Neutralizing anti-TL1A monoclonal antibodies attenuate these effects, reducing inflammation severity and reversing colonic fibrosis with reduced colonic fibroblast activation and lower expression of CTGF, TGFβ1 and IGF-120,21.