IMMUNOMODULATORY ROLE OF MELATONIN - SPECIFIC BINDING-SITES IN HUMAN AND RODENT LYMPHOID-CELLS

This paper reviews the evidence that supports the hypothesis of the ex istence of specific binding sites for melatonin on immune cells. These binding sites have been described in human blood lymphocytes and gran ulocytes, and thymus, spleen, and bursa of Fabricius from different ro dents and birds. The dissociation constant values of these binding sit es are in the 0.1-1 nM range, suggesting that melatonin may play a phy siological role in lymphocyte regulation. Moreover, melatonin binding sites appear to be modulated by guanine nucleotides. Therefore, in add ition to other mechanisms described for the regulation of immune funct ion by melatonin, a direct mechanism of regulation can be involved via binding of melatonin by immunocompetent cells.