Absence of a role for interleukin-13 in inflammatory bowel disease.

IL-13 has been implicated in the pathogenesis of ulcerative colitis (UC), and may have a role in animal models of gut fibrosis. We studied the involvement of IL-13 in inflammation and fibrosis in UC and Crohn's disease (CD). Intestinal biopsies and anti-CD3/CD28- or anti-CD2/CD28-stimulated lamina propria mononuclear cells from UC and CD patients and control subjects were cultured, and IL-13, IL-4, IL-5, IL-17A and IFN-γ production was measured. Mucosal IL-13-producing cells were characterised by flow cytometry. Gut explants from strictured CD, non-strictured CD and healthy donors were cultured ex vivo, and secreted IL-13, IL-1β and collagen were measured. IL-13 production by mucosal explants and activated lamina propria mononuclear cells did not differ between CD, UC and control subjects, and was at least a log lower than IFN-γ and IL-17A. IL-13-producing cells, and in particular natural killer T cells, were uniformly low in all groups. IL-4 and IL-5 were undetectable in culture supernatants. Explants of CD strictures produced low amounts of IL-13, whereas IL-1β and collagen were elevated. We could not confirm that UC or strictured CD are associated with elevated IL-13 production. These data suggest that an anti-IL-13 Ab would not be an appropriate therapeutic strategy in inflammatory bowel disease.