MIYA, MARCUS AND PHELPS 



Ambient Temperatures 

 Number of 21® C 2° C 2° C 



(grouped) (grouped) (single) 



Organisms immu- immu- immu- 



normal nized normal nized normal nized 



Table III. Effect of chronic cold stress (2° C) on mortality of mice challenged with 

 Klebsiella pneumoniae . Animals maintained for 45 days, and immunized at noted 

 temperatures. •? day mortality (dead/total). 



trol groups of mice were kept at 21° C. The results in Table II show 

 that immunization protected the grouped animals. In contrast, the 

 immunization procedure was less effective in mice singly-caged. 

 The nonchallenged stress controls placed at 2° C did not die when 

 grouped, but some (10 per cent) did when singly caged, suggesting 

 that huddling of animals enables a more favorable outcome when 

 animals are acutely stressed by low ambient temperatures. 



Chronic exposure experiments . Two groups of mice were placed 

 at 2° C and 21° C for periods of 45 days before being immunized. One 

 week after the last immunizing injection, the mice were challenged 

 with varying numbers of viable K. pneumoniae. The results in Table 

 ni show that mice were significantly protected by the immunization 

 procedure. The titer of agglutinin antibody formed by mice chron- 

 ically exposed to 2° C was comparable to that formed by animals 

 kept at 21° C. It is interesting that no significant differences in 



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