Characterization of Natural Killer Cells With Antileukemia Activity Following Allogeneic Bone Marrow

To identify cells with potential antileukemia activity following bone marrow transplantation. we have monitored immunologic reconstitution in a patient with acute lymphocytic leukemia in second remission who received intensive chemotherapy and total body irradiation followed by infusion of albogeneic histocompatible marrow. Prior to transplantation. donor bone marrow cells were depleted of T lymphocytes by in vitro treatment with anti-Ti 2 monocbonal antibody and rabbit complement. In the first 3 weeks following bone marrow transplantation, the predominant regenerating mononuclear cell population in peripheral blood exhibited a phenotype characteristic of natural killer (NK) cells. After 4 weeks, T lymphocytes became predominant, but NK cells persisted. Cultured peripheral blood lymphocytes obtained i 2 weeks posttransplant were able to display significant cytotoxicity against leukemic blasts that had been cryopreserved at the time of relapse 5 months prior to bone marrow transplantation. To further characterize those cells with antileukemia activity, we