Isolation and characterization of an immunomodulatory protein (APP) from the Jewʹs Ear mushroom Auricularia polytricha

A new immunomodulatory protein (APP) was purified from the fruiting body of an edible Jewʹs Ear mushroom, Auricularia polytricha, by extraction using 5% cold acetic acid in the presence of 0.1% 2-mercaptoethanol, followed by ammonium sulfate fractionation, DE-52 and MonoQ anion-exchange chromatography. As determined by electrophoresis techniques, the molecular mass of APP is around 13.4 kDa and its pI is approximately 5.1. APP is a simple protein without carbohydrate, and can agglutinate mouse red blood cells. APP alone activates murine splenocytes, markedly increasing their proliferation and gamma-interferon (IFN-γ) secretion, and presents no cytotoxicity in vitro. Although murine splenocytes are stimulated by the mitogen concanavalin A (ConA), APP suppresses their proliferation in a dose-dependent manner. APP (5–20 μg/ml) also enhances the production of both nitric oxide (NO) and tumor necrosis factor-alpha (TNF-α) by LPS-induced RAW 264.7 macrophages. These findings suggest that APP is an immune stimulant and can strengthen the immune response of its host.