Effects of experimental psychological stress on distribution and function of peripheral blood cells

Fifty male subjects (aged 24 to 55 years) were subjected to a mild and potentially uncontrollable interpersonal stress situation. They were asked to solve a difficult puzzle. Subsequently they were requested to explain their solution to "another subject," actually a confederate to the researchers. The confederate frustrated the subjects' explanation efforts. Care was taken that neither solving nor explaining of the puzzle was successful. The experimental situation induced mild psychological strain as documented by mood changes in the experimental group when compared with a control group of 36 male subjects. Peripheral blood was drawn by an indwelling catheter just before, directly after, 15 minutes after, and 30 minutes after the stress situation. Numbers of leukocytes, lymphocytes, monocytes, T-cell subsets, natural killer (NK) cells, and B-cells were determined. As functional assays we used in vitro proliferative responses of T- and B-cells to mitogenic stimulation (PHA and PWM) and to an antigen cocktail. The potential influences of health- and biobehavioral variables were taken into account in the analyses, as well as incidental differences in initial mood or immunological baseline. The results replicated and expanded on previous research. In contrast to controls, experimental subjects showed a significant increase in numbers of NK cells after the stress-period, returning to baseline values after 15 minutes of rest. A similar effect was shown on T-suppressor/cytotoxic cells and, inversely, on T-helper/suppressor ratio, but these effects could be attributed to changes in the numbers of CD8+CD57+ cells. No effects were observed on proliferation. From the results we conclude that the effects of a short lasting mild psychological stressor are mainly restricted to cells of the NK cell population.