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Comparative in vivo and in vitro activation of human natural killer cells by two recombinant alpha-interferons
Abstract:
Natural killer (NK) cell activation by two interferon-alpha subtypes, interferon-alpha A and interferon-alpha D, was examined in vitro and in vivo in eight cancer patients. When assessed in vitro, NK cells in six of eight patients lysed K562 target cells to a greater extent when incubated with interferon-alpha A (1 ng/ml) than with the same concentration of interferon-alpha D. However, when patients were evaluated collectively, no significant difference was detectable in the effectiveness of the two subtypes in enhancing NK cell activity. Patients received the same interferons given as four injections which were randomized with respect to subtype and were separated by intervals of six or more days. NK cell activity was consistently elevated in peripheral mononuclear cells sampled 24 hr but not seven days after injection as compared to peripheral mononuclear cells sampled just prior to each injection (p less than 0.001 for both subtypes). At a given dose level, both interferon subtypes resulted in comparable NK cell activation. However, a negative correlation existed between the amount of interferon administered and the magnitude of enhancement (p less than 0.05). In 16 separate paired determinations, there were eight in which NK cell activity was lower after the second injection of an interferon dose than after the first injection of the same dose (15 or 45 micrograms, irrespective of subtype), and eight in which the alternate pattern occurred. Thus, repeated injection in the same patient of one or the other dose resulted in no consistent changes in the extent of NK cell stimulation. Since the two interferons have a 20-fold difference in specific antiviral activity for human amnion cells and up to an 80-fold difference in human fibroblasts, either different mechanisms are involved in antiviral and NK cell-stimulatory activity, or activities of these two subtypes for cells of different histogenesis vary. Greater NK cell-stimulatory activity therefore occurred at the lowest tested doses, a dose which was less than 10% of previously reported maximally tolerated doses of these interferons.