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-ordin ated series of metabolic changes following invasions by pathogens. The changes are designed to destroy the pathogen. The response is charact erized by fever, proteolysis in peripheral tissues, acute phase protei n and antioxidant synthesis, and enhancement of the activity of the im mune 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 h ave a profound effect upon the production and actions of cytokines. Pr otein energy malnutrition, dietary n-3 polyunsaturated fatty acids and vitamin E suppress cytokine production and actions. An opposite influ ence is exerted by n-6 polyunsaturated fatty acids, poor antioxidant d efence, and supplementation of the diet with protein and branched chai n amino acids. The synthesis of acute phase proteins and glutathione i s dependent upon the adequacy of dietary sulphur amino acid intake. Th e consequences of the modulatory effects of previous and concurrent nu trient intake on cytokine biology are depletion of resources and damag e to the host, which ranges from mild and temporary to severe, chronic or lethal.