Immunomodulatory effect of Schisandra polysaccharides in cyclophosphamide-induced immunocompromised mice

As a strategy to prevent the well-known immunosuppressant effects of cyclophosphamide (Cyp), the immunomodulatory effects of the polysaccharide extract of the fruit of Schisandra chinensis (Turcz.) Baill. were investigated in the present study. The crude Schisandra polysaccharide (SCP) was obtained by water extraction and alcohol precipitation methods. The total carbohydrate, uronic acid and protein contents were determined using the phenol-sulfuric acid, m-hydroxydiphenyl and Bradford method, respectively. The monosaccharide composition of SCP was determined by high-performance liquid chromatography. ICR mice were randomly divided into control, model, low-dose SCP (0.4 mg/10 g), medium-dose SCP (0.8 mg/10 g) and high-dose SCP (1.6 mg/10 g) groups. The mice in the SCP groups were intragastrically administered SCP once a day for 21 days and those from the control and model groups were administered the same volume of distilled water. Subsequently, the mice in the model and SCP groups were intraperitoneally injected with Cyp (20 mg/kg) once a day for 5 days. The mouse leukocyte count in the peripheral blood as well as thymus and spleen indexes were determined, and the phagocytic function of macrophages was estimated using a carbon clearance test. The thymus and spleen were histomorphologically observed. The levels of tumor necrosis factor-α and interferon-γ were measured by ELISA. Furthermore, antibody formation and spleen lymphocyte proliferation were measured by the serum hemolysin and the MTT method, respectively. The apoptotic rate of splenic lymphocytes was determined by flow cytometric analysis. The results indicated that SCP prevents Cyp-induced impairment of the cellular, humoral and non-specific immunity, and may be an auxiliary immune enhancer for the prevention of immune hypofunction.