Described herein is the use of a non-agonist ligand, particularly an antibody, specifically binding to GM-CSF or one of CD116, CD131 and the GM-CSF receptor composed of CD116 and CD131 for use in treatment of leukemia in a patient having undergone allo-HCT or in treatment of other complications arising as a consequence of hematopoietic cell transplantation from an immunologically non-identical donor.