The effect of spikelets of Miscanthus sinensis Andersson (M. sinensis) on IgE-mediated biphasic cutaneous reactions was investigated in BALB/c mice. Mice were passively sensitized by an intravenous (i.v.) injection of monoclonal anti-dinitrophenol IgE antibody (anti-DNP IgE mAb), or actively by an intraperitoneal (i.p.) injection of DNP-derivatized ovalbumin (DNP-OVA) plus aluminium hydroxide gel(Alum) as an adjuvant. Skin reactions were elicited by an epicutaneous challenge of dinitrofluorobenzene (DNFB) and occurred biphasically with peak responses at 1 and 24 h in both animal models. The administrations of a nondialysable water extract of M. sinensis within 2 h before or after DNFB challenge via oral or i.p. route significantly inhibited the biphasic cutaneous reactions in passively and actively sensitized mice. The inhibitory effect was much stronger than those of a glucocorticoid, prednisolone, and a histamine release inhibitor, amlexanox, as positive controls. The active component(s) was predominantly located in the glycoprotein fraction by gel chromatography. In the ears of DNFB-challenged mice, this fraction suppressed the accumulation of inflammatory cells, including mast cells and neutrophils/macrophages. In addition, the biphasic ear swelling was also improved by an administration of the glycoprotein fraction 24 h before active sensitization. These findings indicate that the glycoprotein fraction of M. sinensis was able to inhibit not only the IgE-mediated allergic inflammatory reaction but also the IgE formation. Thus, this fraction may be a useful antiallergic therapy.
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