Introduction 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 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, β7 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 β7 was increased (p = 0.02) and expression of CCR 9 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
Disclosure of Interest J. Landy Grant/Research Support from: The Broad Foundation, H. Al-Hassi: None Declared, E. Mann: None Declared, S. Peake: None Declared, P. Ciclitira: None Declared, J. Nicholls: None Declared, S. Clark: None Declared, S. Knight: None Declared, A. Hart: None Declared
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