The objective of this study was to evaluate the immunomodulatory effects of the purified glycyrrhiza polysaccharides (GP) on the activity of macrophages. A purified fraction of water-soluble polysaccharides, with estimated molecular weight of 10 kDa, was isolated from Glycyrrhiza uralensis Fish using ion exchange and size exclusion chromatography. The results indicate that GP increased the pinocytic activity, the production of nitric oxide (NO), interleukin-1 (IL-1), IL-6 and IL-12 in a dose-dependent manner. The production of IL-1 was induced by GP at a dose of 10 microg/mL; but, NO, IL-6 and IL-12 was significantly induced at 100 microg/mL. A time-dependent enhancement showed that the production of IL-1, NO and IL-12 were significantly increased within 6 h. Superoxide anion (O(2)(-)) production by macrophages from GP-treated mice was higher than that of cells from untreated mice. Moreover, cells from both untreated and treated mice responded to phorbol 12-myristate 13-acetate (PMA) treatment; however, the O(2)(-) production was higher in the cells from treated mice than that of cells from untreated mice. Our data suggest that the beneficial therapeutic effects of GP may be attributed partly to its ability to modulate macrophage immune functions.