Natural killer activity and low-affinity E rosettes in acute leukemias

Natural killer (NK) activity was investigated in 16 patients with acute leukemia in complete remission and in 19 normal subjects. Peripheral blood lymphocytes from the great majority of the patients failed to kill the K562 target cell in a short-term chromium release assay. Nevertheless, the number of cells with NK membrane features (i.e. low-affinity receptors for sheep red blood cells) was close to the normal value. Good levels of NK activity were found in only 2 patients, namely those who had the longest complete remission in their cytological groups. NK activity was also tested in two preleukemic individuals and found normal.