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Background Crohn’s disease (CD) is a chronic inflammation of the human gastrointestinal tract. Intestinal conventional dendritic cells (cDC) maintain the balance between immunity against pathogens and tolerance towards nutrients and commensals. However, there is not much information about DC composition, phenotype and function in the human gut in CD. Methods Human intestinal resections were obtained from patients with ileocolonic CD and proximal colonic cancer. Both inflamed and non-inflamed tissue was obtained from the ileum and colon from CD patients. The non-affected tissue from the proximal (terminal ileum) and distal (proximal colon) sides of the colonic cancer resections (minimum 10cm distance from the tumor) constituted the reference tissue. Tissue was disaggregated and cDC and macrophages enriched by flow-sorting. Human intestinal cDC were identified within singlet viable leukocytes as CD14-CD64-HLA-DR+CD11c+. Type 1 cDC (cDC1) were defined as CD103+SIRPα- while type 2 cDC (cDC2) and identified as SIRPα+ and further divided into subsets based on the expression of CD103. Macrophages were identified within singlet viable leukocytes as CD14+CD64+HLA-DR+. All three cDC subsets and total macrophages were used to stimulate allogeneic CD4+ naïve T-cells which were further characterized by flow cytometry. Results All 3 human intestinal cDC subsets from non-CD controls were able to stimulate naïve T-cells as opposed to intestinal macrophages. Indeed, stimulated T-cells produced IL-10 and co-expressed FoxP3, being this capacity increased in both CD103+ subsets (CD103+SIRPα- and CD103+SIRPα+). Moreover, all three ileal cDC subsets stimulated T-cells more efficiently than their paired colonic counterparts, although the acquired T-cell profile did not differ among tissues. None of the cDC subets, on the contrary, induced the expression of IFNγ or IL-17 on stimulated T-cells. Referred to CD patients, all three colonic cDC subsets were more stimulatory than their counterparts from the control tissue, while CD103+SIRPα+ cDC from the inflamed ileum primed the generation of IL-17+ responding T-cells. Conclusion All human intestinal cDC subsets prime the generation of regulatory FoxP3+ and IL-10+ T-cells. This capacity was increased in both CD103+SIRPα- and CD103+SIRPα+, in agreement with the regulatory functions attributed to CD103+ cDC. All ileal cDC subsets were also more stimulatory than their colonic counterparts. Nevertheless, colonic cDC from CD patients were more stimulatory that non-CD controls, rendering CD103+SIRPα+ cDC from the inflamed tissue in CD with a higher capacity to generate Th17 cells, which suggests that their regulatory functions can be reshaped by the inflamed tissue microenvironment.

P067 Human intestinal CD103+SIRPα+ conventional dendritic cells from patients with Crohn′s disease prime IL-17+ T-cells