Brain Immune Pathways Regulating Immunological Function and Conditioned Immune Responses

A basic assumption of the study of central nervous system (CNS)-immune interactions is that the immune system can signal the brain and that the brain can subsequently modify peripheral immune function. The existence of a regulatory pathway from the immune system to the CNS and back to the immune system suggests that the phenomena of conditioning of immune responses may be explained through the action of classical immunoregulatory lymphokines such as IL-1 on humoral and neural regulatory pathways. Bi-directional communication between the central nervous system and the immune system was first proposed by Besedovsky and colleagues. In their model, products of the immune system released from stimulated immune cells signal the brain which consequently induced a response that down-regulated immune function. The impact of CNS signalling on various components of the immune system has been demonstrated through various behavioral conditioning studies.