SPECIFIC AND NONSPECIFIC RESISTANCE 



Temperature Treatment Mortality ratios at lU days 



(grouped) (single) 



210 C 



2/10 



H/IO 



2® C Zymosan 3/10 u/10 



7/10 

 1/10 



Table VII. Effect of acute cold (2^ C) on mortality of mice challenged intraperi- 

 toneally with I LD^q* of Klebsiella pneumoniae. Unacclimatized animals immunized 

 or treated and challenged at room temperature, then placed at noted temperatures. 

 *1 LDcQ of K. pneumoniae = 68 organisms per mouse as determined by method of 

 Litchfield and Wilcoxon (1949). 



mice is not significant. It should be mentioned here that mice kept 

 at 21° C in groups or caged singly did not show any differences in 

 mortality ratios as determined by preliminary experiments, and 

 therefore the results obtained with the mice kept at 21° C in groups 

 can serve as controls for the mice kept as individuals at 2 C. 



The results presented in Table VII summarize the mortality 

 ratios obtained when mice are subjected to acute cold stress fol- 

 lowing challenge with 1 LD^q of K. pneumoniae. Again, specific 

 immunization afforded the best protection against the induced in- 

 fection when mice were subjected to acute cold stress. However, 

 the mice kept in groups were better protected than mice caged 

 individually and subjected to low ambient temperatures. The mice 

 treated with zymosan and kept at 21° C showed no mortality, but 

 the mice receiving the same treatment and placed at 2° C, whether 



175 



