Suppression of allergic reactions in ovalbumin-sensitized mice by yam storage proteins dioscorins.

To study the biomedical functions of dioscorins isolated from various species of Dioscorea, we investigated their antiallergic potential using an OVA-induced allergy mouse model. All the dioscorins suppressed allergic reactions by decreasing the serum IgE and histamine levels. The serum IFN-gamma and IgG2a levels increased in all the dioscorin-treated mice. The spleen cells from the dioscorin-treated mice also exhibited an up-regulation of IFN-gamma secretion in response to ConA stimulation. Although dioscorins did not affect the IgG1 levels, the IL-5 levels decreased to basal levels in mice treated with dioscorins of D. alata or D. japonica and in most of the lymphoid cells of the dioscorin-treated mice in response to ConA stimulation. The decrease of IgE and histamine levels was concomitant with an increase in IFN-gamma and IgG2a levels and with a decrease in IL-5 levels, suggesting that dioscorins suppressed the OVA-induced allergic reactions, possibly through modulating an imbalanced Th1/Th2 immune response.