Immune regulatory effect of green tea.

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Abstract We examined the anti-allergic effect of epigallocatechin-3-O-(3-O-methyl) gallate (EGCG3″Me) and epigallocatechin-3-O-(4-O-methyl) gallate (EGCG4″Me) isolated from Japanese or Taiwanese tea (Camellia sinensis L.) leaves. These O-methylated catechins strongly inhibit mast cell activation and histamine release after Fc epsilon RI cross-linking through the suppression of tyrosine phosphorylation of cellular protein kinase (Lyn) and the suppression of myosin light chain phosphorylation and high-affinity immunoglobulin E (IgE) receptor expression via binding to the 67 kDa laminin receptor. A double-blind clinical study on subjects with Japanese cedar pollinosis or perennial allergic rhinitis was carried out. At 11 weeks after starting ingestion, during the most severe cedar pollen scattering period, symptoms (i.e. nose blowing and itchy eyes) were significantly relieved by "Benifuuki" green tea containing 34 mg/day of EGCG3″Me compared with a placebo "Yabukita" green tea that did not contain EGCG3″Me. One consecutive month of ingestion of "Benifuuki" green tea was useful for the reduction of some symptoms caused by Japanese cedar pollinosis and did not affect any normal immune responses in subjects with Japanese cedar pollinosis. In addition, the "Benifuuki" green tea was found to significantly relieve the symptoms of perennial rhinitis compared with the placebo "Yabukita" green tea. Based on the investigation of the effects of cultivars, tea crops, and manufacturing methods, green or semi-fermented teas made from fully-matured "Benifuuki" from the second crop should be consumed. The green tea components strictinins and theogallin showed anti-allergic action by inhibiting histamine release through suppressing the biosynthesis of IgE. It was reported that epigallocatechin (EGC) and polysaccharides in tea leaves had immunostimulating activities. Oral administration of a mixture with a high EGC ratio (1:2 to 3=epigallocatechin gallate (EGCG/EGC)) resulted in greater immunoglobulin A production by murine Peyer's patch cells. The EGCG/EGC ratio in a 4°C green tea extract was around 1:3 to 4, whereas in a 100°C extract, it was around 1:0.7. It was identified that EGC-induced phagocytosis can be blocked by catalase and an inhibitor of transient receptor potential melastatin 2. Moreover, it was found that a crude tea polysaccharide from immature tea leaves included a considerable amount of RNA as compared with that from mature tea leaves and increased the phagocytic activity in macrophage-like cells through Toll-like receptor 7.