Effect of dietary protein depletion on nonspecific immune responses and survival in the guinea pig

Abstract

Protein-calorie malnutrition in humans reduces the effectiveness of the immune response to bacterial infections as measured by delayed cutaneous hypersensitivity reactions and the migration and killing activity of polymorphonuclear neutrophils. To investigate the role of protein-calorie malnutrition in increasing susceptibility to Pseudomonas infections, healthy guinea pigs were protein depleted. After 2 to 3 week of consuming a protein-deficient diet, a decreased clearance of bacteria from the blood by the reticuloendothelial system, an increased uptake of ⁵⁹Felabeled Pseudomonas in the liver, bone marrow, lungs, and kidneys (p < 0.05), and an increased mortality to Pseudomonas pneumonia (p < 0.01) were observed. This suggests that the defect in host defense is due, in part, to an inability of the circulating polymorphonuclear leukocytes to kill Pseudomonas. This possibility was supported by the in vitro demonstration of a reduced bactericidal activity of peritoneal phagocytes (p < 0.01). It is concluded that during dietary protein depletion, the effectiveness of the killing system of polymorphonuclear neutrophils is severely diminished. This may partially explain the observed high mortality in P pneumonia.