IDO1 and inflammatory bowel disease: Our data indicated that (i) after an initial increment of IDO1 expression in the acute inflammatory phase, the protein levels and the enzyme activity drop during the milder chronic phase of the disease; (ii) mice treated during the chronic phase with NAS show improved mucosal healing; (iii) IDO1 expression and activity correlate with the severity of mucosal inflammation in patients with IBD; (iv) the response to VDZ and UST treatment is associated with a reduction of intestinal level and systemic activity of IDO1 in IBD patients.