systems. Perhaps the most important interaction relates to immune activation of the hypothalamic-pituitary-adrenal axis via cytokines. Stimulation of this counter-regulatory response plays a critical role in preventing the host from mounting an excessive defense response against "inflammatory stress". Because of these interactions, regulatory relationships exist whereby behavioral stimuli and inflammatory stress can ultimately modulate the function of the immune system.
The influence of biological rhythms on the immune system is presented in Chapter 20. Biologic rhythmic behavior has been characterized in levels of circulating white blood cells and subsets of these cells, cytokines and their inhibitors, and in the humoral immune response, although circadian time dependence of human responses to vaccination is less well documented. Some of the rhythms affecting the immune system are genetically fixed, but in certain frequencies (e.g., circadian) the rhythm may be adjusted in its timing by periodic environmental factors such as light-darkness, activity-rest pattern, temperature, and for some parameters, the timing of food intake. Many of these rhythms have potential major significance to the military.
Finally, Chapter 21 provides a summary of the workshop presentations, identifying those issues of importance to the military and identifying the issues that the CMNR would consider in their report.