Recent studies in our laboratory demonstrated the suppression of immunoglobulin E (IgE) production by green tea extract (GTE) in U266 cells. However, the effects of GTE or one of its components (EGCG) on IgE production by human peripheral blood mononuclear cells (PBMC) are unknown. PBMC (1.5×10 6) obtained from serum IgE+, allergic asthmatic patients, were cultured±GTE (1-100ng/ml) or purified EGCG (0.5-50ng/ml), and IgE levels were determined on day 10 by enzyme-linked immunosorbent assay (ELISA). High levels of IgE were detected in supernatants of the PBMC cultures on day 10. When GTE was included in vitro, IgE production by PBMC was suppressed on day 10, compared with control. Purified EGCG included in vitro also suppressed IgE production, but at lower levels, compared with control. This study demonstrates that GTE and its major catechin, EGCG, have immunoregulatory effects on human IgE responses.
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