The Downregulation of Mast Cell Activation Through the Suppression of the High-Affinity IgE Receptor Expression by Green Tea Catechin Egcg

摘要

IgE-mediated stimulation of mast cells and basophils is an important initial event in the IgE-dependent allergic reactions. The crosslinking of allergen-specific IgE bound to the high-affinity IgE receptor FceRI expressed on these cells with multivalent allergens results in a release of bioactive chemical mediators such as histamine, proteases, chemotactic factors and arachidoic metabolites. Therefore, FceRI is required for mast cells and basophils to initiate the IgE-mediated allergic reaction suchas atopic dermatitis, bronchial asthma, and food allergy. The FceRI is a multisubunit receptor with a ligand binding alpha subunit, a signal modifying membrane-tetraspanning subunit, and a homodimeric disulfide-linked y subunit that provides the signaling ability of this receptor. Among the three sub-units forming the FceRI, the a chain is the specific component of FceRI that mostly extends out to the extracellular region and directly binds to IgE. The study using a chain-deficient mice demonstrated that IgE was unable to bind to the cell surface of mast cells thereby failing to induce degranulation through IgE-binding. Thus, it is expected that the IgE-mediated allergic symptoms may be attenuated by downregulating the FceRI expression in mast cells and basophils.