Interferon activation of "pre-spontaneous killer" (pre-SK) cells and alteration in kinetics of lysis of both "pre-SK" and active SK cells.

Interferon augments spontaneous killer cellular cytotoxicity (SKCC). This modulation may be vital in both tumor resistance and host viral defenses. To date, whether increased numbers of effector cells or activation of individual effector cells is responsible for this augmentation has not been established. Using a single cell assay where SK killing is directly visualized by the reading of trypan blue uptake at various time points by effector-target cell conjugates plated in agarose gel, we measured in vitro alterations in percentage of conjugate formation, number of active SK cells, and kinetics of SK cell lysis at the single cell level after 1 hr of interferon incubation. After interferon, there is no difference in number of cells that bind K-562 targets. This augmentation of cytotoxicity is due to both recruitment of new effector cells and an activation of the lytic process of both the new and already active SK cells.