T-cells are causally involved in the pathogenesis of inflammatory bowel disease (IBD). The
tryptophan-metabolizing enzyme indoleamine 2, 3-dioxygenase (IDO) regulates T-cell
proliferation and survival. We show in this report that IDO mRNA is markedly induced in
lesional colonic biopsies of IBD patients. IDO is primarily expressed in CD123+
mononuclear cells infiltrating the submucosal areas of the inflamed lesions. In Crohn's
disease (CD), IDO is also strongly expressed in perifollicular regions of lymphoid follicles …