A tea catechin suppresses the expression of the high-affinity ige receptor FcεRI in human basophilic KU812 cells

Human basophilic KU812 cells express the high-affinity IgE. receptor FcεRI, which plays a central role in the IgE-mediated allergic response. The effect of several major tea catechins, (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, (-)-epicatechin gallate, and (-)-epigallocatechin gallate (EGCg), on the cell surface expression of FcεRI in KU812 cells was studied. Flow cytometric analysis showed that only EGCg was able to decrease the cell surface expression of FcεRI after a 24 h treatment in a dose-dependent manner. Moreover, immunoblot analysis revealed that the total cellular expression of the FcεRI α chain decreased upon treatment with EGCg. FcεRI is a tetrameric structure comprising one α chain, one β chain, and two γ chains. The level of mRNA production of each subunit in KU812 cells was investigated. KU812 cells treated with EGCg expressed lower levels of FcεRI α and γ mRNA than nontreated cells. These results suggest that EGCg has an ability to down-regulate FcεRI expression, and this suppressive effect may be due to the down-regulation of FcεRI α and γ mRNA levels.