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* = Presenting author

P087. Dendritic cell subsets in the maintenance of gut health and response to bioactives

J. Schulthess1, C. Arancibia1, T. Fenton2, M. Travis2, F. Powrie1, 1John Radcliffe Hospital, Translational Gastroenterology Unit, Oxford, United Kingdom, 2Collaborative Centre for Inflammation Research, University of Manchester, Manchester, United Kingdom

Background

Commensal bacteria and food antigens can potentially trigger immune responses in the gastrointestinal tract. A subset of intestinal dendritic cells (DC) bearing the CD103 molecule and the avb8 integrin is critical in prevention of harmful immune reactions and maintenance of intestinal health in mice. These DC can activate the cytokine TGFb, and metabolise vitamin A into its active form retinoic acid and induce regulatory T-cells in murine models. However, whether similar populations of DC are present in humans is not known. We have identified a specific DC subset in humans whose function is to maintain intestinal health by inducing regulatory T cells. Additionally, we have shown how dietary bioactives affect these cells and their specific biomarkers.

Methods

Lamina propria lymphocytes were isolated from intestinal tissue and stained with a panel of antibodies directed to molecules expressed in DC. Monocyte derived DC were generated by incubating CD14+ monocytes with a cytokine cocktail containing IL-4 and GM-CSF. Gut-like DC were derived from monocytes by adding retinoic acid to the cultures.

Results

We have newly identify the CD141+ human gut DC subset as a potentially important functional gut DC population involved in the maintenance of intestinal homeostasis. We have analysed gut-associated pathways in blood-derived DC and also determined how more abundant blood-derived DC can be differentiated to acquire a gut phenotype. To this end, we have successfully differentiated blood monocyte-derived DC (MoDC) into gut-like CD103+ DC in the presence of the vitamin A metabolite retinoic acid or butyrate. MoDC cultured with TGFb or FLT3L are unable to promote CD103 or CD141 expression on MoDC. By contrast, CD103+ RA-induced DC are CD141+ and CD1c−ve and thus appear ‘gut-like’. We find that retinoic acid-induced DC displayed increased production of the anti-inflammatory cytokine IL-10 and decreased production of the pro-inflammatory cytokine TNFa. Moreover retinoic acid-induced DC and butyrate-induced DC exhibited reduced expression of the activation markers CD80, CD83 and CD86 when stimulated with LPS compared to classical MoDC. Importantly, stimulation of naive CD4 T cells with a polyclonal stimulus in the presence of RA-induced DC leads to the preferential induction of FOXP3+ regulatory T cells.

Conclusion

We have identified distinct subsets of DC in the human intestine, which are potentially important in promoting intestinal homeostasis. Additionally, we find that in vitro generated CD103+ DC express tolerogenic molecules suggesting these cells have important functional properties of gut DC. These results describe novel mechanisms with which to generate gut-like DC with tolerogenic properties.