Augmentation of natural killer activity of human peripheral blood lymphocytes by human leukocyte interferon: characterization of the augmented activity.

The characteristics of natural killer (NK) activity of human peripheral blood lymphocytes treated with human leukocyte interferon (HuIFN-alpha) were compared with those of the untreated original NK activity. HuIFN-alpha, at a concentration of 50 IU/ml or more, augmented the NK activity against BALL-1, Daudi, and Namalwa target cells. On the other hand, the augmentation was less evident for the activity against Raji and Molt-4 cells. Original NK activity was detected mainly in the fraction that passed through a nylon wool column. Nylon-retained cells, however, could be activated by the addition of HuIFN-alpha to express activity against BALL-1. The activity of the nylon-passed fraction was augmented by HuIFN-alpha as well as that of unfractionated cells. NK cells could be activated by HuIFN-alpha under calcium-free conditions that allow NK cells to bind but not to lyse the target cells; augmented cytotoxicity was observed when calcium was added 2 hr later. This suggests that the augmentation of NK activity by HuIFN-alpha may have resulted from an increase in the number of NK cells.