Natural killer activity in patients with acute myelocytic leukemia.

The natural killer activity of isolated mononuclear cell populations of acute myelocytic leukemia (AML) patients in remission and relapse was compared with that of mononuclear cells obtained from normal subjects. The target cells consisted of 51Cr-labeled blast cells of the K-562 cell line, which was originally obtained from a patient with chronic myelocytic leukemia in blast crisis. The natural killer activity of lymphocytes from AML patients in remission was similar to or higher than that of normal subjects. A marked depression in this function was associated with relapse, as well as with heavy combined chemotherapy. It is concluded that natural killer activity assessed in vitro is an accurate indicator of the clinical stage of AML patients.