Regulation of rat natural killing. I. Inhibition of cytolysis and activation by protein synthesis inhibitors.

Rat splenic natural killer (NK) cell activity against 51Cr-labeled YAC-1 or TMT-081 tumor cells can be augmented by culturing at 37 degrees C for 18 h. The protein synthesis inhibitors, cycloheximide and emetine, inhibited such NK activation and also inhibited NK lysis when added directly to the NK assay. Both drugs also inhibited conjugation of effector cells to target cells. The inhibitory effect of cycloheximide on both the NK lysis and NK activation was reversible while that of emetine was irreversible. Both agents were able to inhibit 3H-amino acid incorporation at the concentrations that inhibited NK activity and activation. Culture-activated NK cells were found to be less susceptible to inhibition by cycloheximide and emetine.