Issue 1
Vol. 42
2000

Behaviourally conditioned immunosuppression: Mechanisms and biological relevance
M. S. Exton, J. Westermann, M. Schedlowski

Bi-directional interactions between the central nervous system (CNS) and immune system are demonstrated by the modification of immune function using behavioural conditioning. Despite numerous reports describing this phenomenon, little advance has been made in revealing the mechanisms or biological relevance of this interesting behavioural paradigm. Here we report that the immunosuppressive effects of cyclosporin A (CsA) can be behaviourally conditioned in rats using saccharin as a gustatory conditioned stimulus. In conditioned animals the mitogen-induced lymphocyte proliferation in the spleen is significantly suppressed, which is paralleled by an inhibition of IL-2 and IFN-g synthesis by splenocytes. The CNS effects these peripheral alterations in immune function via direct neural innervation of the spleen, as surgical denervation of the spleen completely abrogated the immunological effects. Furthermore, the conditioned changes in immune function are biologically relevant, as they prolong the survival time of a transplanted heart. Thus, during conditioning the CNS learns to reinstate at demand a CsA-like immunosuppression via splenic innervation. The ability of the conditioned changes to produce a prolongation of heart allograft survival offers promise that such paradigms have the potential to possibly one day be used as a supportive therapy for controlling immune functions.

Key words: behavioural conditioning, immunosuppression.

Psychologische Beiträge, Band 42, 2000, S. 118-129

Dr. M. Exton
Division of Medical Psychology
Medical Faculty
University of Essen
D-45147 Essen