ABSTRACT
Understanding of the immune system and its varied functions has advanced considerably in recent years. Underlying physiological mechanisms and the complex multicellular interactions that are required to maintain homeostasis provide endless research opportunities. In the past, the immune system was considered to be an isolated organ system with limited physiological interaction with other body systems. Recent studies have clearly demonstrated that this is not the case. The immune system is far more complex than anyone ever anticipated. Its interactions with many other systems, including the endocrine and nervous systems, for example, have made it difficult to determine the full relevance and mechanisms of immune alteration. Immune function appears to be influenced by stress, neuromediators, hormones, and various psychological factors. In addition to immunomodulatory disturbances, effects on behavior, reproduction, or other disease states, may be under a degree of immune regulation. Such associations have led to the establishment of several new subdisciplines, including immunoteratology and psychoneuroimmunology (Madden and Felten, 1995). Nutritional status and aging have also been identified as important factors with respect to immune function.
