Assessment of Immune Function
THE ROLE OF NUTRITIONAL IMMUNE function is of considerable interest to the military. Of particular interest are the optimization and assessment of immune function in the field as well as the development of improved methods of immunization, including oral vaccines. Chapters 20 and 21 review techniques for the assessment of abnormal immune function, while Chapter 22 focuses on the development of vaccines targeted toward mucosal immunity.
In Chapter 20, the use of plasma and urinary cytokine measurements to document the presence of inflammatory stress is assessed, focusing on tumor necrosis factor-a (TNF-a), interleukin-1 (IL-1), and IL-6 because they are overlapping and distinct mediators that affect nearly every organ system in the host. The author concludes that plasma TNF-a and IL-1 are not reliable indicators of inflammation, but plasma IL-6 levels often seem to be elevated in inflammatory processes, correlating with physiologic parameters. While urinary TNF-a and IL-1 levels often are not detected in the circulation or in the urine of most surgical patients, they are increased after ''eccentric" exercise. Under the same conditions, urinary IL-6 is increased. The plasma and urinary measurements of IL-6 in particular can be used for detecting metabolic stress.
Chapter 21 focuses on defining measurable, functional parameters for studying abnormalities of the immune system related to malnutrition, stress, and
aging. Although the multiple components involved in immune response make this difficult, longitudinal studies incorporating measurement of serum immunoglobulin concentrations and humoral responses to vaccines and boosters, and determination of serum and urinary levels of select cytokines involved in inflammatory processes and immunoregulatory processes have shown promise. Functional assays of immune function, such as delayed hypersensitivity skin tests or natural killer cell function tests, are ideal but not always practical.
Because the effects of exposure to infectious agents and toxins can significantly impair military performance, safe and effective immunization is a priority, as the discussion of mucosal immunity in Chapter 22 indicates. The gastrointestinal and respiratory tracts are the route of entry into the body for many pathogens that may alter nutritional status, and the mucosal immune system is the point of defense against these pathogens. A better understanding of mucosal immunology, coupled with progress in biotechnology and molecular genetics, may lead to the optimization of oral vaccine administration using antibodies and antigens.