Methods and compositions are provided to augment the conversion of mixed hematopoietic cell chimerism to complete donor cell chimerism following allogeneic hematopoietic cell transplantation (HCT), where such transplantation may be utilized for treatment of cancer such as leukemia and lymphoma or for other conditions requiring reconstitution of the hematopoietic system, e.g. treatment of anemias, thalassemias, autoimmune conditions, and the like. The present invention improves on conventional DLI by utilizing a composition of substantially purified donor memory CD8+ T cells as DLI following allogeneic HCT, where the cells are administered at a suitable time following transplantation. The methods provide for a more complete donor chimerism, and have the further benefit of killing tumor cells without GVHD. The memory CD8+ T cells may include one or both of central and effector memory T cells, usually both.