Shock-induced modulation of lymphocyte responsiveness and natural killer activity: differential mechanisms of induction.

The present study was designed to determine the influence of signaled shock on splenic natural killer (NK) activity and nonspecific T-lymphocyte mitogenic responsiveness. Furthermore, experiments were conducted to examine possible mechanisms mediating this suppression. The results demonstrate that a single session of signaled shock induces suppression of splenic NK activity and T-cell response to the mitogens concanavalin A (Con A) and phytohemagglutinin (PHA). However, the suppression of mitogenic responsiveness was attenuated after five daily sessions of shock, while NK activity remained suppressed. The suppression of NK function was prevented by administration of naltrexone prior to the shock session indicating mediation by opiate receptors. However, naltrexone did not prevent the shock induced suppression of mitogenic responsiveness to Con A or PHA. Diazepam was not effective in preventing the shock-induced suppression of mitogenic responses or NK activity. Collectively, these results demonstrate that mononuclear cell populations in the spleen are differentially affected by the same stressor and that the immune alterations are mediated via different pathways.