TNFSF15 and Crohn ileitis: However, a major difference was that the ileitis found in the recently published Tl1a Tg mice appeared to be mainly attributed to Th2/IL-13 effector pathway [16], [17], whereas we observed a higher production of IFN-γ from the Tl1a Tg mice generated in this study (Fig. 11B and 12A).