DLK1 and immune system disorder: Although the cellular and molecular mechanism setting off the immunosuppressive in vivo effect of MSCs in T cell development and generation of the humanized NSG mice remains unclear, considering therapeutic impacts of MSCs in translational researches, including infectious and regenerative immune diseases, and functional importance of Dlk1-Notch signaling in cell fate decision, our data and humanized NSG mice might contribute to the development of therapeutics targeting various human diseases as a potential animal model system.