Activation of the anti-tumor effector cells by Radix bupleuri

Radix bupleuri, the root of Bupleuri spp., Chinese medicinal herbs used for the treatment of influenza, malaria and menstrual disorders, were extracted with hot water and separated into five different fractions (RB, RBI, RBII, RBIII and RBIV) by stepwise alcohol precipitation. One of these fractions, RBI, was then fractionated into RBIa and RBIb by gel filtration using G-100 Sephadex. These two fractions were further purified into RBIai, RBIaii and RBIbi, RBIbii fractions respectively by ion-exchange chromatography using DEAE-Sephadex. Each of these fractions is a heteropolymer consisting mainly of carbohydrate and varying proportions of protein and uronic acid. RBIaii was found to show strong anti-tumor activities in sarcoma-bearing mice. Mechanistic studies showed that RBIaii exhibited a potent activating effect on the cytotoxic activity of macrophages, NK and LAK cells against tumor cells. In addition, RBIaii could increase the number of tumor infiltrating lymphocytes (TILs) in the tumor site of WEHI-164-bearing mice. Furthermore, RBIaii could induce the release of interferon-gamma by lymphocytes in vitro.