Abstract
The influence of repeated exposure to low or high ambient temperatures on the immune response was studied in mice following a single injection of sheep red cells. Male dd-strain mice, weighing 15 to 19g were raised in aclimatic chamber at 25±1°C and 60%RH, with light from 0700 to 1900 (LD 12:12). After three weeks acclimation, the mice were randomly divided into control and experimental groups, and both groups were immunized with sheep red cells (6.6×107/g body weight). The experimental group was then exposed repeatedly to temperatures of 8°C, 33°C, 36.5°C. Both control and experimental mice were sacrificed to collect sera and spleen samples.
Hemmagglutination (HA) and hemolytic reaction (HR) tests were carried out. Plaque-forming cells (PFC) in the spleen were counted, and antibody formation was compared to that in the control group.
The following results obtained:
1) The immune response was suppressed in mice exposed over eight hours a day to 36.5°C temperatures. However, when the duration was fixed at four hours a day, the immune response increased, as the number of periods of exposure increased (i.e. 4hrs ×1, 2hrs ×2 and 1hrs ×4).
2) No significant change in the immune response was found in mice exposed to 33°C temperatures.
3) Exposure two hours a day to 8°C temperatures increased the immune response, while exposures of over eight hours a day suppressed it. A daily exposure of four hours enhanced the immune response only slightly over that of the control group. The results suggest that the turning point at which the immune response begins to increase or decrease falls within an exposure to 8°C of between four and eight hours. When the duration was fixed at four hours a day, the immune response increased as the number of periods of exposure increased, as in the case of 36.5°C.
The above experiment has demonstrated that the effects of exposure to heat or cold on the immune response depends not only on the temperature level, but also on the frequency of its change.
