Background Crohn’s disease (CD) and ulcerative colitis (UC) are potentially progressive diseases. Few data are available on the prevalence and the factors associated with mild inflammatory bowel diseases (IBD). Aim Our aim was to assess the natural history of mild CD and mild UC and to identify predictive factors of mild evolution over the long term. Methods Retrospective study of IBD patients registered in the database of the university hospital CHU of Liège, Belgium. Mild CD was defined as an inflammatory luminal disease (no stricture, abdominal or perianal fistulae) requiring no immunomodulator (IM), anti-TNF and no surgery. Mild UC was defined as no requirement for IM, anti-TNF and no colectomy. Results Four hundred and seventy-three CD and 189 UC were included (median follow-up: 13 and 11 years respectively). At 1 year, 147 patients had mild CD. At 5 years and the maximum follow-up, 56% and 13% patients still had mild CD, respectively. At 1 year, 142 patients had mild UC. At 5 years and the maximum follow-up, 72% and 44% still had a mild UC, respectively. Factors associated with long-term mild CD and UC were older age at diagnosis and absence of corticosteroids in the first year. In UC proctitis location was associated with mild UC. Conclusions In this cohort, 90% of CD patients and 3/4 of UC with mild disease at 1 year lost their mild disease status over time. An old age at diagnosis was predictive of the persistence of a mild CD and UC.

The aim of our study was to determine the effect of a rectocolonic preimmunization with ovalbumin on the systemic immune response induced by a subsequent subcutaneous injection of this antigen in Balb/c mice. One rectocolonic, but not intragastric, administration of 25 mg of ovalbumin induced a detectable increase in serum anti-ovalbumin antibody level. The level reached was however much lower than after subcutaneous injection. Both intragastric and rectocolonic immunization with ovalbumin induced specific systemic cellular tolerance. However, after rectocolonic, but not intragastric, preimmunization there was no systemic humoral tolerance to this antigen. These differences in systemic immune responses after rectocolonic or intragastric administration of ovalbumin could be due to different stimulation of the systemic immune system or to differences between the colonic and small bowel mucosal immune system, which remain to be elucidated.