IDO1 and colitis: In agreement with this is the fact that inflammation was reduced in Stat1−/− mice following DSS treatment (Bandyopadhyay et al., 2008), and an Ido1−/− mouse (Ido1 is up-regulated in S839I mice; Fig. 6, C and G) shows a reduced severity to DSS-induced colitis (Shon et al., 2015).