The learned immune response: Pavlov and Beyond
The latest scientific evidence has demonstrated that the placebo effect stems from highly active processes in the brain that are mediated by psychological mechanisms such as expectation and behavioral conditioning. During the last years we have developed several protocols of behavioral immunoconditioning in rats, mice and humans. When saccharin taste as a conditioned stimulus (CS) and the immunosuppressive drug Cyclosporine A as an unconditioned stimulus (UCS) is paired in rats during acquisition, re-exposure to the CS during evocation induces a significant inhibition of the proliferative capacity of splenic lymphocytes as well as interleukin-2 and interferon-gamma production and cytokine mRNA expression. These behavioral conditioned immunosuppressive effects are mediated on the efferent arm via the splenic nerve, noradrenaline and beta-adrenoceptor dependent mechanisms. In addition, the insular cortex, the amygdala and the ventromedial nucleus of the hypothalamus have been identified as essential neuronal structures for this associative learning processes. The conditioned immunosuppression is of biological relevance, since behavioral conditioning significantly prolonged the survival of heterotopic transplanted heart allografts and behaviorally conditioned immunosuppression has also been demonstrated in humans. Moreover, the immunosuppression induced by behavioral conditioning can be intensified by increasing the number of acquisition as well as evocation trials, further indicating the potential feasibility of conditioning procedures in clinical settings.
- Prof. Dr. Manfred Schedlowski
- Prof. Dr. Michael Schaefer