Augmentation of human K-cell activity with interferon.

Our laboratory recently reported that interferon (IF) could augment human antibody-dependent cellular cytotoxicity (ADCC) and cytotoxicity by natural killer (NK) cells. Although there is general agreement that IF can boost the activity of human NK cells, two laboratories have reported a failure to boost ADCC. We have therefore examined in more detail the effects of IF on human ADCC. We have found, by several lines of evidence, that IF can indeed appreciably augment the activity of K cells, the subpopulation of lymphocytes that mediate ADCC: (1) human leucocyte IF, purified to homogeneity, boosted ADCC: (2) IF augmented ADCC against target cells that were completely resistant to NK activity; and (3) the ADCC activity of leukaemic cells from a patient with chronic lymphocytic leukaemia (CLL) which lacked any detectable NK activity was boosted by IF. These results are consistent with the hypothesis that human NK and K cells are the same subpopulation of lymphocytes and that the mechanisms regulating their activity are similar. However, the absence of NK activity in the CLL patient strongly supports the idea that not all FcR-positive cells are NK and that ADCC effectors devoid of NK may exist. However, further evidence is required to analyse this point.