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.