Primer on Immune Response and Interface with Malnutrition

The mammalian immune system has evolved an innate component to identify classes of pathogens (e.g., viruses, types of bacteria, parasites) and respond with specific effector mechanisms to clear such infections. When the innate immune system cannot clear infections, the adaptive immune system develops pathogen-specific immunity that employs similar effector mechanisms to specifically target a particular pathogen in order to clear the initial infection and prevent further infections. The immune system protects the host at a nutritional cost which can be substantial in the case of frequent or severe infections. This cost is due both to the effects of the pathogen on host tissues and to the inflammatory response to infection that cause decreased food intake, nutrient malabsorption, nutrient loss, increased nutrient metabolism, and altered nutrient transport and storage. Malnutrition can compromise host defenses and increase the frequency or severity of infections. Most nutrients are required for adequate immunity, and examples are provided for several specific nutrients.