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

Summary

At concentrations as low as 5 × 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 C57B1/6 mouse spleen cells when added to cultures as late as 48 hr after antigen addition. GA-induced suppression was reversed by 5 × 10-⁵ M 2-mercaptoeth-anol (2ME) added at the same time as, or up to 48 hr after, antigen and was reversed less efficiently by adherent-cell supernatant (ACS). GA also suppressed mitogen-in-duced DNA synthesis of C57B1/6 T lymphocytes, and 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 lipo-polysaccharide (LPS)-induced B-lympho-cyte DNA synthesis. The data suggest that GA selectively suppresses a macrophage (MØ)-dependent T-lymphocyte function(s).