Donor leukocyte transfusions for leukemic relapse.

Treatment of recurrent leukemia after bone marrow transplantation with the transfusion of lymphocytes from the marrow donor has been successful in a majority of patients with chronic myelogenous leukemia and a minority of patients with acute myeloid leukemia and myelodysplastic syndrome. It has been disappointing in patients with acute lymphoblastic leukemia and in advanced stages of chronic myelogenous leukemia. In chronic-phase chronic myelogenous leukemia remissions were of good quality and the actuarial relapse rate was less than 20% at 3 years. In acute leukemias remissions were less durable. Graft-versus-host disease and marrow aplasia were the major complications of this form of treatment. In patients with marrow aplasia hematopoiesis could be restored by infusion of donor marrow without further conditioning treatment. Preceding or concomitant treatment with interferon alpha is not essential for a response, but the exact role of interferon alpha remains to be determined in a randomized study. Similarly, the best time for treatment remains to be defined. Treatment of cytogenetic and molecular recurrence of chronic myelogenous leukemia is most effective in preventing marrow aplasia, but a few patients may be treated unnecessarily, for some cytogenetic recurrences may remit spontaneously. The mechanism of the graft-versus-leukemia reaction is still not clear. Effector cells and target antigens remain to be defined. Observations are compatible with a graft-versus-host reaction directed against minor histocompatibility antigens presented at the cell surface of hematopoietic cells, but reactions against leukemia-specific antigens are possible. Future studies will focus on differences of reactions against possible leukemia-specific antigens and histocompatibility antigens on hematopoietic cells and cells of other organs.