Not so long ago, it was believed that the brain is totally devoid of immunologic reactions, that cytokines derived from activated leukocytes serve only as communication molecules between leukocytes and that the immune system is regulated solely by intrinsic mechanisms. One by one, these old-time, traditional views have fallen by the wayside as neuroscientists, endocrinologists and pharmacologists have begun to explore immunology. The old view was that the immune system is autonomous because it neither affects nor is it affected by other physiologic systems. The new view is that cells of the immune system are inextricably linked with other physiological systems, including the neuroendocrine, cardiovascular, reproductive and central nervous systems (CNS). Changes in one system evoke changes in the other, and it is likely that communication loops have evolved between cells of the immune system and those of other tissues to coordinate and regulate functional activities aimed at preserving homeostasis during inflammation. The integrated view of immunophysiologists that cells of the immune system interact with the entire body, rather than existing as a separate physiologic system that operates autonomously, should help to unravel a number of mysteries in immunoregulation, such as the well-recognized redundant and pleiotropic properties of cytokines. Unfortunately, very few of these ideas have been incorporated into studying immunity of domestic animals. A complete understanding of immunobiology will be achieved only after this new field of immunophysiology is integrated into current immunological thinking. The purpose of this short article is to describe new discoveries which provide insights into how leukocytes discriminate between self and non-self by enlisting the aid of the neuroendocrine and CNS and to document what is known about the immunophysiology of pigs.
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