Viscotoxin-free aqueous extracts from European mistletoe (Viscum album L.)stimulate activity of human granulocytes

Background: Extracts from European mistletoe (Viscum album L., VAL) are use d for complementary cancer treatment. Viscotoxins (VT) and whole plant ex-t racts with high amounts of the VT have been shown to stimulate functional a ctivity of granulocytes Materials and Methods: We stimulated neutrophils from healthy donors in vit ro with aqueous VT-free VAL extracts and mistletoe lectins (ML) in the pres ence of E.coli and studied phagocytosis (via incorporation of FITC-labelled E.coli) and respiratory burst (via oxidation of dihydrorhodamine 123 to rh odamine 123) by flow cytometry. Results: The VT-free VAL extract significantly stimulated granulocyte activ ity and this effect correlated with the content of the ML, although the ML exerted no influence at relevant concentrations. Co-incubation of the cells with VAL in the presence of VT further increased granulocyte response. Conclusions: Fi-om these data it is suggested that (1) a non-VT non-ML comp onent of the VAL extracts activated granulocytes and (2) different activati on pathways may be involved in the stimulation by the whole plant extinct a nd the VT.