Stress and immune responses. III. Effect of restraint stress on delayed type hypersensitivity (DTH) response, natural killer (NK) activity and phagocytosis in mice.

Several experiments were conducted to evaluate the influences of restraint stress on cell-mediated immune events in mice. Delayed type hypersensitivity response to sheep red blood cells was inhibited by the stress, regardless of the timing of restraint stress loading. The activity of phagocytosis of macrophages in vitro and in vivo were measured by using the zymosan-particle uptake method and the carbon clearance test, respectively. Both activities were decreased in restraint-stressed mice. The suppressed carbon clearance rate in stressed mice, however, was recovered by the transfusion of serum from normal mice. Natural killer activity in spleen cells was decreased to 30-50% of the control in stressed mice. However, no suppressor cells which could inhibit NK activity existed in the spleen from stressed mice. These results show that the restraint stress suppresses various kinds of cell-mediated immune events, which might play an important role in anti-tumor immunity.