Effects of Viscum album L. on cyclophosphamide-treated peripheral blood mononuclear cells in vitro: sister chromatid exchanges and activation/proliferation marker expression.

Based on recently published data, Viscum album L. (VAL) extracts have been shown to provide a DNA stabilizing effect which seems to be restricted to the peripheral blood mononuclear cells (PBMC). We have now investigated whether VAL exerts effects of cellular protection for phytohemagglutinin-activated PBMC treated with cyclophosphamdie (CP) in vitro. The addition of VAL resulted in a slight reduction of CP-induced sister chromatid exchanges of cultured PBMC from healthy individuals. The incubation with CP significantly reduced the expression of the low affinity interleukin-2 receptor (IL-2R alpha chain) and of transferrin receptor (TfR) on PHA-stimulated T lymphocytes. The addition of 10 micrograms/ml VAL was protective against the CP-induced depression of IL-2R alpha chain and TfR expression on these cells. The simultaneous addition of CP and purified VAL components, such as ML I, ML II/III, and viscotoxins did not significantly change expression of IL-2R alpha chain and TfR on T cells. Thus, so far undefined VAL components might be responsible for the observed protection effects of the whole plant extract. The results presented here should encourage investigation of this drug, which might become an interesting adjuvant in cancer therapy.