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 used for complementary cancer treatment. Viscotoxins (VT) and whole plant extracts with high amounts of the VT have been shown to stimulate functional activity of granulocytes.

MATERIALS AND METHODS

We stimulated neutrophils from healthy donors in vitro with aqueous VT-free VAL extracts and mistletoe lectins (ML) in the presence of E.coli and studied phagocytosis (via incorporation of FITC-labelled E.coli) and respiratory burst (via oxidation of dihydrorhodamine 123 to rhodamine 123) by flow cytometry.

RESULTS

The VT-free VAL extract significantly stimulated granulocyte activity, 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

From these data it is suggested that (1) a non-VT non-ML component of the VAL extracts activated granulocytes and (2) different activation pathways may be involved in the stimulation by the whole plant extract and the VT.