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P093. Dendritic cell characteristics in pouchitis

J. Landy1, E. Ronde2, H. Omar Al-Hassi2, E. Mann2, S. Peake1, P.J. Ciclitira3, R.J. Nicholls4, S.K. Clark5, S. Knight2, A.L. Hart1, 1St Mark's Hospital, IBD Unit, London, United Kingdom, 2Antigen Presentation Research Group, Imperial College, London, United Kingdom, 3St Thomas' Hospital, Gastroenterology, London, United Kingdom, 4Imperial College, Department of Biosurgery and Surgical Technology, London, United Kingdom, 5St Mark's Hospital, Colorectal Surgery, London, United Kingdom

Background

The role of dendritic cells (DC) in inflammatory bowel disease is increasingly recognised for their function in regulating intestinal immune responses. To our knowledge there are no previous studies of DC in pouchitis. We aimed to characterise changes in DC in pouchitis that may underlie the dysregulated immune response to the pouch microbiota.

Methods

Mucosal biopsy samples were taken from ulcerative colitis patients with pouchitis (n = 14) and ulcerative colitis patients without pouchitis (n = 10). Lamina propria DC were isolated by collagenase digestion. DC were identified as an HLA DR+, lineage (CD3, CD14, CD16, CD19, CD34) population. DC expression of TLR 2 and 4, CCR9, β 7 and CD40 were measured by multicolour flow cytometry. The t-test was used for statistical analysis.

Results

DC expression of TLR 2 and 4 were both significantly elevated in patients with pouchitis compared with non-pouchitis patients (p = 0.007 and 0.008). In pouchitis patients, DC expression of β 7 was increased (p = 0.02) and expression of CCR9 was decreased (p = 0.02). DC expression of CD40 was increased in patients with pouchitis (p ≤ 0.0001).

Conclusion

In pouchitis, DC are activated and upregulate expression of microbial recognition receptors. In addition, DC expression of gut homing markers is elevated in pouchitis with a more colonic homing marker profile. Similarly to other IBD, DC are likely to be key in the initation and perpetuation of the inflammatory response to the dysbiosis of the pouch microbiota.