demonstrate in a mouse model of GI-GVHD that IL-12 from ileal macrophages, IFN-γ from lymphocytes, as well as sensing of microbiota-derived TLR ligands induces MHC-II upregulation on intestinal epithelial cells, which then present allo-antigens to donor T cells to induce lethal GVHD (215). This evidence concerns the gene IFNG and graft versus host disease.