CXCR4 and graft versus host disease: There are also many promising pre-clinical studies focused on the potential application of immune cells in controlling GVHD, such as umbilical cord blood (CB) derived stromal cells [58], ex vivo expanded CB CD4 + CD25+ Foxp 3+ regulatory T cells [59], as well as CXCR4-transduced MSCs, which maintained their immunosuppressive capacity and showed enhanced migration capacity in vitro, thus controlled the occurrence of GVHD more effectively [60].