Biol. Pharm. Bull. 29(7) 1366—1371 (2006)

widely eaten and prescribed around the world. It is belonged to the Agaricaceae family and is popularly known as “Himematsutake” in Japan. In Brazil, this mushroom is used as a traditional medicine for the prevention of cancer, diabetes, hyperlipidemia, arteriosclerosis, and chronic hepatitis. Recently, it has been reported that Agaricus blazei has the anti-tumor, immunomodulatory, anti-mutagenic, anti-oxidant, and anti-bacterial activities. However, it has not been cleared whether it prevents allergic diseases in experimental model. In general, immediate-type hypersensitivity reactions that involve asthma, allergic rhinitis, urticaria, and anaphylaxis are mediated by mast cells. In response to the IgE-dependent and IgE-independent stimuli, mast cells elicit degranulation, which results in releasing various mediators, such as histamine and an array of inflammatory cytokines. Histamine, a main content of granules in mast cells, exerts many effects related to the immediate phase of allergic inflammation including vasodilatation, increased vascular permeability, tissue edema, contraction of bronchial and intestinal smooth muscle, and increased mucus production. Mast cell degranulation can also be elicited by the basic secretagogues. The most potent secretagogues include the compound 48/80, which is a mixed polymer of phenethylamine cross-linked by formaldehyde and a high dose of which induces almost a 90% release of histamine from mast cells. Thus, compound 48/80 has been used as a direct and convenient reagent to study the mechanism of allergy and anaphylaxis. In this study, we demonstrate the Agaricus blazei water extract (ABWE) inhibits compound 48/80-induced systemic anaphylaxis-like reaction, ear swelling response, and passive cutaneous anaphylaxis-like reaction in mice. We also show that ABWE reduces anti-dinitrophenyl (DNP) IgE-mediated passive cutaneous anaphylaxis. Afterward, the inhibitory effect of ABWE on compound 48/80-induced mast cell activation is elucidated, as reported previously.