Natural killer cells in chronic leukemia. Function and markers

Twenty-two patients with chronic lymphocytic leukemia (CLL) and 14 patients with chronic myelogenous leukemia (CML) were studied with respect to natural killer (NK) cell activity and related cell markers (Leu 7 and Leu 11b). Significantly reduced NK cell activity was detected in peripheral blood from the patients with CLL. Similarly, a reduced number of cells with the markers Leu 7 and Leu 11b (CD 16) were detected in the same patients. Removal of the leukemic cells by centrifugation of cells forming rosettes with mouse erythrocytes led to an augmented, but not fully normalized, NK activity. This indicates that the low NK activity in CLL partly may be due to overgrowth of leukemic cells. However, in spite of the lymphocytic infiltration, the NK cell activity in the bone marrow of CLL patients did not differ significantly from that of normal controls. The patients with CML in the chronic phase as well as patients in the accelerated or blast phase also had a reduced NK activity. The finding that patients in the chronic phase had a reduced NK activity and normal numbers of Leu 11b (CD 16) positive cells, together with no detectable blasts in the peripheral blood, indicates that patients with CML may have an inherent NK cell defect. The highly reduced activity found in patients with the accelerated/blast form may in addition partly be due to overgrowth of leukemic cells. This low NK activity may be of importance in the development of chronic leukemia.