It has been demonstrated that the administration of progenipoietin-1 (a synthetic granulocyte colony-stimulating factor/Flt-3 ligand molecule) to donors in an allogeneic bone marrow transplantation model generated MDSCs, which upon transfer suppressed the initiation of graft-versus-host disease (GVHD) in recipients by inducing a population of MHC class II-restricted, interleukin 10 (IL-10)-producing T-reg (55). Here, FLT3 is linked to graft versus host disease.