Inhibitory effect of the water extract of spikes of Miscanthus sinensis on IgE formation in mice.

The effects of four different plant extracts of the spikes of Miscanthus sinensis, Phragmites communis, and Imperata cylindrica var. major, and of the spikelets of Coix lachryma-jobi on IgE antibody formation were investigated in mice. The IgE antibody titer was tested by the passive cutaneous anaphylaxis (PCA) method in rats. Of these, the water extract of M. sinensis showed an appreciable inhibitory effect on IgE formation. Furthermore, an undialyzable fraction of the water extract with a relative molecular mass of more than 50,000 d, designated as MSIS, showed the most potent inhibitory activity on IgE formation. MSIS was also a potent inhibitor of IgE formation when given intraperitoneally or intranasally to mice the day before injection of dinitrophenyl (DNP)-ovalbumin (OVA) antigen in both the primary and secondary immune responses. Moreover, MSIS clearly suppressed on-going IgE antibody formation in both primary and secondary immune responses.