ABSTRACT
The biological existence and propagation of a species is the result of selective environmental pressures on individual diversities. The effect of stress on immune reactivity and its consequential impact on susceptibility to various diseases constitutes, perhaps, the most extensively studied topic in research about the mechanisms and physiopathologic relevance of the immuno-neuroendocrine system. Most interesting, melatonin was also effective in restoring resistance mechanisms against a sublethal infection with encephalomyocarditis virus in mice that were exposed to acute restraint stress. In the course of studies concerning the immunoregulatory properties of melatonin the people addressed the question of its mechanism of action. A virus detected by the immune system will produce an acute activation of immunocompetent cells which may finally modulate the pineal melatonin response to a given photoperiod which, in turn, will influence the specific immune response along with other melatonin-sensitive neuroendocrine mechanisms.
