The effects of stressor predictability on lymphocyte proliferation in humans

Abstract

To demonstrate the effects of predictable and unpredictable stressors on immune function, 36 male subjects were randomly assigned to complete ten trials of either a predictable or unpredictable cold pressor task or a non-stressful warm pressor control task. The predictable and no-stressor groups were given information about the duration of each pressor trial and a countdown of seconds passed from beginning to end of each trial. The unpredictable stressor group received no information. Self-report, cardiovascular, and biochemical measures were taken throughout the tasks in order to ascertain the effectiveness of the predictability and stressor manipulations. Lymphocyte proliferation to concanavalin A (Con A) and pokeweed mitogen (PWM) were measured before, during and after the tasks. Lymphocyte proliferation to Con A (10/μg/ml) was significantly reduced only in response to the unpredictable stressor suggesting that predictability buffered the effect of the stressor on immune function. Proliferation to PWM followed a similar pattern but was not statistically significant. Blood pressure responses were negatively correlated with proliferation values suggesting that stressor predictability may attenuate stress-associated immune decreases by reducing sympathetic arousal.