Effects of several species of human leukocyte interferon on cytotoxic activity of NK cells and monocytes.

Ten species of purified human leukocyte interferon were tested for their ability to modulate the cytolytic activity of natural killer (NK) cells and the cytolytic and cytostatic activities of monocytes. The interferon species were tested at several antiviral titers and examined for quantitative differences in their ability to modulate immunological function. At the higher doses of interferon (i.e., greater than 500 units) all of the interferon species demonstrated significant augmentation of cytolysis and cytostasis. However, when low levels (i.e., 10-50 units) of interferon were employed, appreciable differences between the various interferon species were seen. A similar pattern of relative potency among the various species of pure leukocyte interferon was seen for augmentation of cytolysis by monocytes and NK cells. In contrast, a different pattern of relative potency was observed for augmentation of cytostasis. These results demonstrated substantial quantitative differences (as much as 100-fold) in the ability of the various species of human leukocyte interferon to induce significant levels of augmentation of these cell-mediated functions. Such results should have significant impact in choosing a specific interferon species for appropriate clinical trials.