Variable sensitivity of lymphoblastoid cells to apoptosis induced by Viscum album Qu FrF, a therapeutic preparation of mistletoe lectin

Background: Viscum album (VA) Qu FrF preparation consists of an aqueous ext ract of Viscum album, the European mistletoe. It has cytotoxic and immunomo dulatory properties that support its usefulness in cancer therapy. However, only little information is available on the interaction between mistletoe lectin (ML) and the humoral compartment of the immune system. Methods: Inhi bition of proliferation of cells was performed by incorporation of H-3-thym idine, and cell viability was assessed by the uptake of propidium iodide. D etection of Bcl-2 and related molecules was performed by SDS-PAGE followed by immunoblotting. Results: We demonstrated that B lymphocyte lines are ins ensitive to VA Qu FrF-induced apoptosis. We showed, using Fas-sensitive and Fas-resistant cell lines, that VA Qu FrF-induced apoptosis is Fas independ ent. In both B and T lymphocytes, treatment of the cells with VA Qu FrF was associated! with decreased levels of Bcl-2 and Bcl-X. Conclusions: Our res ults suggest that B lymphocyte depletion is not involved in the modulation of humoral immunity by ML. These observations should be of value in appropr iate designing of cancer therapy using compounds containing mistletoe extra cts. Copyright (C) 2001 S. KargerAG, Basel.