Psychoneuroimmunology: where are we, where are we going?

We have reviewed briefly the current status of research on central nervous system-immune system interactions, focusing attention on the neural and humoral pathways by which CNS and IS communicate and interact and on the effects of stress and psychiatric illness on immune function. It is evident that CNS-IS communication occurs by direct innervation of lymphoid organs and by means of hormones, neuropeptides and cytokines. There is also clear evidence that humoral substances each of which were thought to be the product of one specific cell type are elaborated and secreted by a variety of cell types. This observation suggests a new unified concept of CNS-IS interactions with mediators of these interactions being produced ubiquitously and acting on cells of the two systems. In examining the effects of stress on IS it has become apparent that stress of various types can have a depressive effect on immune functions, primarily at the level of T lymphocytes and NK cells. This suggests that the defense mechanisms affected by stress are those which are responsible for cytotoxic effector responses. These findings are interesting in that they support older studies implicating stress in the pathogenesis and/or the clinical course of neoplastic diseases. Further support for a role of stress-induced immunodepression in morbidity comes from a very interesting, recent prospective study showing that stress will affect susceptibility to viruses. Finally, exploration of the mechanisms of stress-induced immunodepression, suggests that a variety of mediators which regulate lymphocyte interactions and activation may be affected, perhaps at the level of gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)