The influence of thermal environment on the immune response of mice. (2) Effects of high ambient temperature.

The influence of high ambient temperature on the immune response was studied in mice following a single injection of sheep red cells and following results could be obtained.(1) Mice acclimatized to 33°C or 35°C for 3 weeks produced the same splenic PFC and HA and HR activities as mice kept at 25°C. However, immune responses of the mice acclimatized to 36.5°C were significantly suppressed throughout the whole immunological course.(2) Transfer of mice from 25°C to 33°C ambient temperature just after immunization caused an acceleration in immune response; number of PFC increased in the initial phase of the immune response but decreased in the productive phase as compared to control. In the cases of mice transferred to over 35°C ambient temperature, however, the serum antibody levels as well as a number of PFC were depressed remarkably throughout immune response.(3) In the case of the mice transferred from 33°C to 25°C just after immunization, the number of PFC was apt to be suppressed in the initial phase, but increased in the productive phase of immune response. HA and HR activities of these mice were, however, apt to be suppressed throughout immune response. HA response of the mice transferred 35°C to 25°C was also apt to be suppressed, but the number of PFC of the mice transferred 36.5°C to 25°C was inclined to be higher than control throughout immune response.(4) Temperature shift from 25°C to 33°C or 33°C to 25°C resulted in a corresponding increase or decrease in HA and HR activities as well as number of PFC. Influence of temperature shift was observed most conspicuosly in the case of the shift from 25°C to 33°C 3 days before immunization and in the shift from 33°C to 25°C 1 day before immunization respectively.(5) The effect of repeated heat (36.5°C) or cold (8°C) exposure on the immune response could not be observed clearly.