Pediatric refractory Inflammatory Bowel Disease (IBD) is a chronic inflammatory condition of the gastrointestinal tract, not responsive to current treatments. Since hematopoietic stem and progenitor cells (HSPCs) in the bone marrow display immunomodulatory functions and IL-10-producing regulatory cells regulate gut homeostasis, by combining state-of-the-art strategies for the ex-vivo manipulation and expansion of HSPCs and gene delivery systems to drive HLA-class II-restricted antigen presentation and expression of tolerogenic molecules, the investigators propose to dissect the antigen- (Ag-) presenting capacity of HSPCs and to exploit their tolerogenic potential to induce IL-10-mediated tolerance in the intestinal mucosa of IBD patients. The investigators hypothesize that HSPCs can be engineered using commensal-derived Ags w/wo IL-10 to drive the differentiation of Tr1 cells with the desired Ag-specificity to control intestinal inflammation in IBD. The results of this study will pave the way for defining innovative cell-based approaches for treating refractory pediatric IBD.