Using Ccl19-Cre-driven Dll1 and Dll4 inactivation, we identified a non-haematopoietic SLO stromal cell subpopulation (CD45−CD31−PDPN+CD157+) as the likely cellular source of Dll1/Dll4 ligand in GVHD [66]. This evidence concerns the gene DLL4 and graft versus host disease.