Effects of infection on nutritional status and immunity.

Generalized infectious illnesses cause a highly predictable series of biochemical, metabolic, and hormonal responses. In combinations with fever and anorexia, these responses lead to hypermetabolic losses of cellular constituents and a depletion of body nutrient stores. Concomitantly, infectious processes stimulate a complex series of defensive measures that include both organism-specific immunological responses and an activation of generalized nonspecific defenses. The possible presence and impact of an infectious process must therefore be considered whenever nutrition-immune system interrelationships are studied in experimental animals. In clinical situations, nutritional depletion and weakened host defenses must be recognized as expected sequelae of acute infectious illnesses and, conversely, the presence of development of an infectious process must be anticipated in patients with malnutrition, both before and during their rehabilitation.