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Effects of methanol extract of Astragali Radix (AR) on the immune responses were studied using ICR mice. Mice were divided into 4 groups (10mice/group), and methanol extracts of AR at doses of 0.05, 0.25 and 1.25g/kg were orally administered to ICR mice once a day for 2 weeks. Mice were immunized and challenged with sheep red blood cells (SRBC). The results of this study were summarized as follows; (1) Methanol extract of AR at 0.05, 0.25 and 1.25g/kg didn’t affect the weight ratios of thymus to body, as compared with those in controls, but significantly increased spleen weight ratio. (2) Methanol extract of AR at 0.05 and 0.25g/kg significantly increased hemagglutination titer and splenic plaque forming cells corresponding to humoral immunity, as compared with those in controls, but their enhancements were somewhat lowered at a high dose (1.25g/kg). (3) Methanol extract of AR at 0.05 and 0.25g/kg siginificantly increased delayed-type hypersensitivity reaction resulted from cell-mediated immunity, as compared with those in controls, but not so significant increases were observed at a high dose (1.25g/kg). (4) Methanol extract of AR at 0.05 and 0.25g/kg significantly increased phagocytic activity and the number of circulating leukocyte compared with those in controls, but their enhancements were lowered at a high dose (1.25g/kg). These results suggest that methanol extract of Astragali Radix increased humoral and cell-mediated immune responses, phagocytic activity and the number of circulating leukocyte, dependent upon dose, but inhibited their enhancement effects were decreased at a high dose (1.25g/kg).
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