TNFSF15 and colitis: To evaluate the contribution of direct TL1A-DR3 signaling on fibroblasts to TL1A-mediated fibrosis in vivo, we used the adoptive T cell transfer model of colitis with TL1A over-expressing naïve T cells (Tl1a-Tg) in fibroblast-selective DR3-deficient, Rag−/− mice (Rag−/−Dr3∆Col1a2).