INTERACTIONS BETWEEN THE BRAIN AND THE IMMUNE-SYSTEM

For reasons that are not entirely clear, the neurosciences and immunology evolved without seriosly considering the possibility of interactions between these systems that could mutually influence their respective functions (1). Within the past 10 years, research concerned with the relationships among brain, behavior, and immunity has expanded rapidly. Experiments have reliably documented the effects of behavior on immune function and the existence of unsuspected connections between the nervous and immune systems. Our purpose here is to provide a brief and highly selected overview of some of the evidence that behavioral factors are capable of influencing immune function and to describe some of the neural and endocrine channels of communication that link the brain and the immune system. Although systematic research in psychoneuroimmunology is relatively new, the range of the phenomena that bear on brain-behavior-immune system interactions is quite broad. There is an old and continuing experimental and clinical literature suggesting that immune function can be altered by psychological means, and there are provocative data suggesting that affective states and personality characteristics are associated with differences in immune function. Strategically and practically, such studies are difficult to implement, and unequivocal evidence for such associations does not yet exist. A discussion of these areas is beyond the scope of this review. The present review concentrates on the experimental as opposed to the clinical literature concerning the effects of behavior (including stress) in the modulation of immune responses, and the interactive relationships among neural, endocrine, and immune processes that could lead to an explanation of such phenomena and a greater appreciation and understanding of integrated processes of adaptation.