Restoration of impaired natural killer cell activity of B‐chronic lymphocytic leukemia patients by recombinant interleukin‐2

Natural killer (NK) function in the majority of B‐cell chronic lymphocytic leukemia patients is markedly deficient. This study was undertaken to determine if the biological response modifier interleukin‐2 (IL‐2), which is a potent augmenter of normal individuals' NK activity, could augment the low NK activity in these patients. Peripheral blood lymphocytes (PBL), depleted of B‐cells, from most B‐CLL patients exhibited low natural killer activity against NK‐sensitive K562 cells and against herpes simplex virus (HSV)‐infected lymphoblastoid cell lines (LCL). Incubation of patients' B‐cell‐depleted PBL with recombinant IL‐2 resulted in augmentation of their NK activity against both K562 cells and HSV‐infected cells. Furthermore, whereas large granular lymphocytes (LGL) isolated from CLL patients are deficient in cytoplasmic granules, which are thought to play a role in NK‐cell‐mediated lysis, treatment of patients' LGL resulted in increased granulation by 4 hr after treatment with IL‐2 and showed a concomitant increase in lytic activity comparable to that of normal individuals.