Suppression of Macrophage-Dependent T-Lymphocyte Function(s) by Gallic Acid, a Food Additive Metabolite

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Abstract
At concentrations as low as 5 .times. 10-6 M, gallic acid (GA), a metabolite of the food additives propyl gallate and tannic acid, suppressed the anti-sheep erythrocyte (SRBC) plaque-forming cell (PFC) response of C57Bl/6 mouse spleen cells when added to cultures as late as 48 h after antigen addition. GA-induced suppression was reversed by 5 .times. 10-5 M 2-mercaptoethanol (2ME) added at the same time as, or up to 48 h after, antigen and was reversed less efficiently by adherent-cell supernatant (ACS). GA also suppressed mitogen-induced DNA synthesis of C57Bl/6 T [thymus-derived] lymphocytes, this suppression was reversed by 2ME. GA had no effect on the response of athymic nude mouse spleen cells to the thymus-independent antigen Escherichia coli 0127:B8, and failed to suppress lipopolysaccharide (LPS)-induced B[bone marrow-derived]-lymphocyte DNA synthesis. GA apparently selectively suppresses a macrophage (M.PHI.)-dependent T lymphocyte function(s).