Studies of natural killer cell activity and antibody-dependent cell-mediated cytotoxicity among patients with acute leukemia in complete remission

Low natural killer (NK) cell activity against the K-562 leukemia cell line was observed in patients with acute leukemia in the early stages of remission, i.e., 2-4 months (11.3%±7.95% specific target cell lysis). This parameter was found to be normal among leukemia patients after a longer time in remission (19.53%±7.55%) when compared with healthy donors (18.46%±12.98%). A similar pattern of activity was observed in studies of antibody-dependent cell-mediated cytolysis (ADCC) to the CEM lymphoid tumor cell line in the same group (37.58%±12.4% vs. 51%±6.79% specific target cell lysis). ADCC to chicken red blood cells (CRBC) and to human red blood cells (HRBC) was not significantly different from that for healthy controls at either duration of remission. Nine patients relapsed over a follow-up period of 9 months. They were found to have slightly lower NK activity (14.4%±9.3%) and ADCC to CEM (41.4%±8.5%) than the patients who remained in remission (17.1%±6.8%; 48.7%±9.7%, respectively). These data indicate a lymphocyte deficit which may persist for some time after remission has been induced, and which may be due to the effect of leukemic cell burden or the effect of aggressive chemotherapy.