Gr-1+CD11b+CD11c+ MDSCs effectively prevent GVHD development and maintain antitumor cytotoxicity of allogeneic T cells, while the majority of the in vitro-generated MDSCs expressing Gr-1+CD11b+CD11c− are totally inefficient to dampen GVHD, although they block T-cell expansion in vitro. Here, ITGAX is linked to graft versus host disease.