Conditioned Alterations of Specific Blood Leukocyte Subsets Are Reconditionable

Behavioral conditioning has the ability to produce changes in immune function. However, it is unknown whether conditioned changes of immune function can be recalled on multiple occasions. To address this issue we paired a novel saccharin drinking solution with intraperitoneal cyclosporin A (CsA) injection in rats. Saccharin re-presentation produced a reduction in splenocyte proliferation that mirrored the effect of CsA. Such functional changes were paralleled by a significant conditioned leukopenia in peripheral blood, which opposed the leukocytosis induced by CsA. Using the conditioned leukopenia in blood as a ‘diagnostic window’ of conditioned immunosuppression, the maintenance of CsA-induced changes was investigated by examining blood samples collected repeatedly. Experiments on the same group of animals over a period of 1 year showed that the conditioned leukopenia was reproducible on multiple occasions by reimplementing either the whole conditioning paradigm or reexposure to the saccharin solution only. These results demonstrate that behaviorally conditioned alterations of immune parameters are maintained in subsequent trials, indicating the potential clinical feasibility of behavioral conditioning procedures.