In vivo administration of L-dopa or dopamine decreases the number of splenic IFN gamma-producing cells.

Although dopamine receptors are present on peripheral immune system cells, relatively little is known about the functional role that dopamine may play in immune responses. The purpose of this study was to determine the effects of chronic treatment with L-dopa and dopamine on murine lymphocyte proliferation and cytokine production/release. In vivo treatment with L-dopa resulted in an increase in the proliferative response of splenic lymphocytes to ConA. Spleen cell supernatant concentrations of IL-4 and IFN gamma were not significantly altered following treatment with L-dopa for 5 days. However, the number of IFN gamma-, but not IL-4-producing cells was significantly inhibited by L-dopa. This effect was blocked by co-treatment with a dopamine antagonist. The effect on IFN gamma was replicated by infusion of dopamine. The results suggest that dopamine may have a direct role in regulating immune responses through down-regulation of IFN gamma.