Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) is a curative option for most of hematological malignancies, though the graft-versus-tumor (GVT) effect mediated by immune cells from the donor. However, the use of Allo-HSCT is limited by its toxicity, notably the graft-versus-host disease (GVHD) that is a major cause of non-relapse mortality (NRM). Conditioning regimens dramatically improved during the last fifteen years, with a decrease of both GVHD and NRM rates. Now, disease recurrence after Allo-HSCT is the first cause of treatment failure and remains a concern for approximately 30% of the patients.