MELATONIN INCREASES ANTIGEN PRESENTATION AND AMPLIFIES SPECIFIC AND NONSPECIFIC SIGNALS FOR T-CELL PROLIFERATION

Our preceding results have shown that melatonin administration to norm al and immunodepressed mice increases significantly the antibody respo nse. We also found that melatonin is able to restore the impaired T-he lper cell activity in immunodepressed mice. The present study shows th at melatonin enhances antigen presentation by splenic macrophages to T -cells. This effect is concomitant with an increase in the expression of MHC class II molecules and production of IL-1 and TNF-alpha. Consid ering the role of antigen presentation and cytokine production in the initiation of the immune response, the present findings provide eviden ce for relevant mechanisms that may account for the regulatory role of the pineal gland in immunoregulation.