Biol. Pharm. Bull. 29(7) 1360—1365 (2006)

sensitivity, such as allergy and anaphylaxis. 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 acute phase of immediate hypersensitivity, including vasodilatation, increased vascular permeability, and tissue edema. 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. In general, compound 48/80 initiates the generation of superoxide anion by A-kinase inactivation through decreasing the intracellular cAMP concentration in mast cells. Generated superoxide anion results in the increase of intracellular calcium content, which leads to histamine release from mast cells. Thus, compound 48/80 has been used as a direct and convenient reagent to study the mechanism of allergy and anaphylaxis. Phellinus linteus, an orange color mushroom growing well on mulberry tree, is a well-known fungus of the genus Phellinus in the family of Hymenochaetaceae and has been used as a traditional herb medicine in oriental countries. Proteoglycan isolated from Phellinus linteus has been shown to have anti-tumor and immunomodulatory effects. It has also been shown to alleviate the septic shock induced by the lipopolysaccharide injection in mice and to be involved in the prevention and treatment of autoimmune joint inflammation such as rheumatoid arthritis. Moreover, ethanol extract of Phellinus linteus exhibits potent anti-oxidant and anti-angiogenic activities. Lim et al. have reported that organic solvent extracts of Phellinus linteus suppress IgE production by modulating helper T lymphocytes 1/2 balance in murine splenocytes and mesenteric lymph node lymphocytes. Inagaki et al. have also demonstrated that a boiling water fraction from mycelium of Phellinus linteus inhibits IgE-dependent mouse triphasic cutaneous reaction. However, direct cellular mechanism underlying the mast cell-mediated anaphylaxis-like reaction has poorly been understood. In this study, we have investigated the inhibitory mechanism of water extract from the fruiting body of Phellinus linteus against the anaphylaxis-like reaction and mast cell activation.