THE EFFECTS OF STRESSOR PREDICTABILITY ON LYMPHOCYTE-PROLIFERATION INHUMANS

To demonstrate the effects of predictable and unpredictable stressors on immune function, 36 male subjects were randomly assigned to complet e ten trials of either a predictable or unpredictable cold presser tas k or a nonstressful warm presser control task. The predictable and no- stressor groups were given information about the duration of each pres ser trial and a countdown of seconds passed from beginning to end of e ach trial. The unpredictable stressor group received no information. S elf-report, cardiovascular, and biochemical measures were taken throug hout the tasks in order to ascertain the effectiveness of the predicta bility and stressor manipulations. Lymphocyte proliferation to concana valin A (Con A) and pokeweed mitogen (PWM) were measured before, durin g and after the tasks. Lymphocyte proliferation to Con A (10 mu g/ml) was significantly reduced only in response to the unpredictable stress or suggesting that predictability buffered the effect of the stressor on immune function. Proliferation to PWM followed a similar pattern bu t was not statistically significant. Blood pressure responses were neg atively correlated with proliferation values suggesting that stressor predictability may attenuate stress-associated immune decreases by red ucing sympathetic arousal.