The soy isoflavone equol enhances antigen-specific IgE production in ovalbumin-immunized BALB/c mice.

Although an immunomodulatory role of the soy isoflavone genistein has been demonstrated, the effects of other soy isoflavones on induction of antigen (Ag)-specific immune responses are not known. In this study, we therefore investigated the effects of daidzein and equol on ovalbumin (OVA)-specific T cell and B cell responses in BALB/c mice. Mice that had been treated with 20 mg/kg equol showed a significantly higher level of OVA-specific IgE than control mice. Levels of interferon (IFN)-gamma and interleukin (IL)-4 production were not different between the control and equol groups. However, IL-13 production level in mice administered 20 mg/kg equol was significantly higher than that in control mice. Strong induction of OVA-specific IgE production by equol was also observed in ovariectomized BALB/c mice, suggesting that the immunomodulatory effect of equol is not affected by endogenous estrogen.