IL-2/LAK adoptive immunotherapy is one of new complementary treatments for advanced malignant tumors. This therapy has two main problems: high dose of IL-2 often causes serious side effects and it is difficult to gain enough amount of LAK cells. MPS is a new immunomodulator in cancer immunotherapy. The present study showed that, comparing with IL-2 10(6)U/L only, IL-2 2 x 10(5)U/L plus MPS 0.4mg/L was significantly more effective in activating both the growth of LAK cells and its cytotoxicity against HEP-2 cells. And the ratio of CD25 positive LAK cells cultured in this condition was also higher. This result suggests that MPS plays a role in creasing the membrane receptors of IL-2.