MALNUTRITION AND THE IMMUNE-RESPONSE .2. IMPACT OF NUTRIENTS ON CYTOKINE BIOLOGY IN INFECTION

Interleukins 1 and 6 and tumour necrosis factor orchestrate a co-ordinated series of metabolic changes following invasions by pathogens. The changes are designed to destroy the pathogen. The response is characterized by fever, proteolysis in peripheral tissues, acute phase protein and antioxidant synthesis, and enhancement of the activity of the immune system. Cytokine production is enhanced by free radicals. Damage to the host may occur as a consequence. The deterious actions of these molecules are held in check by sophisticated antioxidant defences and systems which exert feedback control on cytokine biology. Nutrients have a profound effect upon the production and actions of cytokines. Protein energy malnutrition, dietary n-3 polyunsaturated fatty acids and vitamin E suppress cytokine production and actions. An opposite influence is exerted by n-6 polyunsaturated fatty acids, poor antioxidant defence, and supplementation of the diet with protein and branched chain amino acids. The synthesis of acute phase proteins and glutathione is dependent upon the adequacy of dietary sulphur amino acid intake. The consequences of the modulatory effects of previous and concurrent nutrient intake on cytokine biology are depletion of resources and damage to the host, which ranges from mild and temporary to severe, chronic or lethal.