Serotonin and Melatonin Synthesis in Peripheral Blood Mononuclear Cells: Stimulation by Interferon-7 as Part of an Immunomodulatory Pathway

Abstract

Serotonin and melatonin inhibit phytohemagglutinin- (PHA) induced interferon-.gamma. (IFN-.gamma.) production by lymphocytes. In this paper, it is shown that IFN-.gamma.-increased tryptophan uptake by lymphocytes and macrophages led to an enhanced production of serotonin. When IFN-.gamma. and serotonin were added together to a lymphocyte culture, N-acetyl serotonin and melatonin production was increased, whereas the path to 5-hydroxy-indoleacetic acid remained unchanged. Therefore, the stimulated IFN-.gamma. production of serotonin and melatonin by lymphocytes and macrophages and the inhibition of IFN-.gamma. synthesis by these indoleamines suggest a hypothesis for an immunoregulatory circuit.