ENHANCEMENT OF IMMUNE FUNCTION IN MICE FED HIGH-DOSES OF SOY DAIDZEIN

High soy consumption leading to high exposures of soy isoflavones has been associated with a reduced risk of cancers at many sites. As part of a study focusing on the chemopreventive mechanisms, we have investi gated the modulating effects of daidzein, a prominent and more bioavai lable isoflavone in soy foods, on murine immune function. Swiss mice w ere fed daidzein at various doses daily for seven consecutive days. At high doses (20 and 40 mg/kg), daidzein exerted a stimulatory effect o n nonspecific immunity, as shown by increases in the phagocytic respon se of peritoneal macrophages and thymus weight, in a dose-dependent ma nner. Augmentation of spleen immunoglobulin M-producing cells against sheep red blood cells demonstrated an activation of humoral immunity. Enhanced cell-mediated immunity was also observed as increases in lymp hocyte proportion of peripheral blood. However, no significant immunor egulatory effect was Sound when mice were fed 10 mg/kg daidzein. These results demonstrate for the first time that daidzein at high doses en hances several immunologic functions and suggest a novel approach to u nderstanding the mechanism(s) by which soy foods may contribute to obs erved cancer prevention.