Background and aims: Pouchitis is a common complication following formation of an ileal pouch-anal anastomosis [IPAA] after proctocolectomy for ulcerative colitis [UC]. Gut-specific lymphocyte trafficking mechanisms have been identified as players in the pathogenesis of UC. In the present study, we aimed to characterise the presence of lymphocyte subsets expressing gut-homing molecules in pouches and peripheral blood of UC patients with and without pouchitis.
Methods: Biopsy samples and peripheral blood were collected from 29 patients with an IPAA [seven with active inflammation, 22 without inflammation]. Expression of adhesion molecule MAdCAM-1 was assessed using immunohistochemistry, and flow cytometry was used to characterise expression of integrin α4β7, C-chemokine receptor 9 [CCR9], and CD103 on T cell subsets.
Results: MAdCAM-1 expression was significantly increased in case of active inflammation in the pouch. T cells expressing integrin α4β7 were abundant in the pouch mucosa, but the frequency of integrin α4β7-expressing T cells was decreased on CD4+ lymphocytes during inflammation. Co-expression of gut-homing markers CCR9 and α4β7 was more pronounced in biopsies compared with peripheral blood, but was not enhanced upon active inflammation.
Conclusions: Gut-homing T cells are abundant in pouch mucosa, but the classic hypothesis that the chronic inflammatory state is maintained by an accumulation of α4β7-expressing effector T cells is not supported by our data.
Keywords: MAdCAM-1; Pouchitis; integrin alpha4beta7.
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