No abstract

A generalized infectious process leads to a broad and complex array of metabolic responses within the host. Certain of these responses have a direct causal relationship to the interactions of body cells with invading microorganisms or their products, or to specific host defensive mechanisms. Other host metabolic responses have less clearly defined roles although they involve many tissues and seem to be initiated and regulated by certain hormones-like endogenous mediators. These latter responses contribute to the maintenance of body homeostasis, the provision of metabolizable energy to meet increased body needs, and the synthesis of the acute phase reactant serum proteins.

This review describes the scope, complexity, and magnitude of host nutritional responses throughout the course of an infectious process. These responses include prominent changes in nitrogen and protein metabolism, altered rates of carbohydrate and lipid production and utilization, and changes in mineral, electrolyte, trace element, and vitamin metabolism. It is postulated that these responses develop in a relatively predictable sequence which is influenced by the adequacy of host antimicrobial defense mechanisms, the severity and duration of illness, and specific localization of an infectious process within the body. In addition to hormonal regulatory effects, the metabolic and nutritional responses of the host are also influenced by biologically active substances released when host cells participate in phagocytic activity and local inflammatory responses.

No abstract

Malnutrition can have adverse, even devastating effects on the antigen-specific arms of the immune system and on generalized host defensive mechanisms. Protein/energy malnutrition and/or deficiencies of single nutrients that assist in nucleic acid metabolism generally lead to atrophy of lymphoid tissues and dysfunctions of cell-mediated immunity. Deficiencies of single nutrients can impair production of key proteins. Trace element deficiencies are often multifactorial. Essential fatty acid deficiencies can reduce or perturb the synthesis of cytokine-induced eicosanoids. Arginine deficiency can diminish the production of nitric oxide, and deficiencies of antioxidant nutrients can allow increases in the damaging effects of free oxygen radicals. Humoral immunity continues to be maintained, although new primary responses to T-cell-dependent antigens are generally subnormal in both magnitude and quality. Immunological dysfunctions associated with malnutrition have been termed Nutritionally Acquired Immune Deficiency Syndromes (NAIDS). Infants and small children are at great risk because they possess only immature, inexperienced immune systems and very small protein reserves. The combination of NAIDS and common childhood infections is the leading cause of human mortality. NAIDS can generally be corrected by appropriate nutritional rehabilitation, but from a viewpoint highly important to this Workshop, AIDS and NAIDS are intensely synergistic. AIDS-induced malnutrition can lead to the secondary development of NAIDS, with its much broader array of additional immunological dysfunctions. The complex and far reaching insults to the immune system caused by NAIDS, and the synergistic combination of NAIDS and AIDS, thereby hasten the demise of many victims of AIDS. Aggressive nutritional support for children with HIV infections could delay, or lessen, the development of NAIDS and avoidance of NAIDS would improve both quality and length of life.