IL33 and colitis: Although Il33 was not increased in unstimulated citrine+ cells from DSS-treated mice compared to those from control mice (Fig. 4B), ex vivo stimulation with IL-1β increased Il33 expression in citrine+ cells from DSS-treated mice (Fig. 4C), indicating that IL-1β could play a role in the regulation of IL-33 in the colon during colitis.