 One major obstacle to further advancement in the role of bone marrow transplant BMT in hematological malignancies is graft-versus-host-disease GVHD, which can best be prevented by removing T-cells from the donor stem cell product. However, previous experience with T-cell depletion has been associated with an increased rate of engraftment failure and leukemic relapse. Another obstacle is that a large fraction of leukemia and lymphomas afflict older patients who are more prone to GVHD and have co-morbid conditions that prevent them from being a candidate for BMT. 