ABSTRACT
This chapter reviews what is known about the aging immune system. I take the point of view that the study of the aging immune system, as well as of the immune system in general, should be undertaken by viewing the immune system as part of an interactive network of systems whose job it is to maintain homeostasis (i.e., to help the organism make adjustments to environmental changes). Traditionally, this network has included the CNS and the endocrine system and the environmental perturbations have, for the most part, included stimuli that are external to the organism. However, there is no apparent reason why the network cannot be expanded to include each and every system of the organism, ranging from the major histocompatibility complex in man (or the HLA system in mice), which controls the genetic expression of lymphocytes, to the cardiovascular system which, in part, transports peripheral blood lymphocytes to various parts of the body. Nor is there any reason why the stimuli that trigger the action of the network cannot include the introduction of antigenic material. The important point is that, when viewed from this perspective, the immune system not only helps the organism to adapt to environmental changes stemming from the presence of foreign molecules, but it also provides feedback to other parts of the larger network which, in turn, plays important roles in adaptation to environmental change.
