The Effect of Malnutrition on the Inflammatory Response

In the present experiments, Selye's granuloma pouch technique was applied to the study of the effect of host nutritional state on inflammation and the local tissue response. The normal response of well-nourished laboratory rats fed a diet containing 28% protein to the injection of 1% croton oil into a preformed subcutaneous air sac involved the accumulation of hemorrhagic exudate in the pouch lumen and the progressive thickening of the pouch wall, with the proliferation and maturation of fibroblasts and the eventual laying-down of collagen. In malnourished animals, fed a diet containing only 3-4% protein but adequate in all other nutrients, the above reactions were inhibited. This inhibitory effect was encountered after a relatively short period of deficiency and became more marked as the deficiency progressed. No consistent, clear-cut difference was seen in the leukocytic or neutrophilic response between the two dietary groups after the injection of 1% croton oil. A significantly higher proportion of accidental bacterial infections was found in the pouches of malnourished animals than in those of well-nourished animals. This was considered to be a possible consequence of the depressed inflammatory response in malnourished rats. The advantages of the granuloma pouch as an experimental procedure for the study of local reactions to different noxae, and the influence of malnutrition on these reactions have been discussed and suggestions for future studies presented.