Immunomodulatory activity of a peptide isolated from Viscum album extract (NSC 635 089).

A peptide isolated from Viscum album extract (Iscador) has been earlier reported to have cytotoxic and tumour reducing activity. Administration of the peptide (2 micrograms/ml) was found to produce increased natural killer cell activity (NK-activity) in the normal animals and tumour bearing animals. The peak activity was observed on the 3rd day after the administration of the peptide. Administration of the peptide also stimulated antibody dependent cellular cytotoxicity (ADCC) which was expressed maximally on the fourth day. There was also an increase in antibody forming cells in the spleen, and antibody titers were increased in the animals treated with the peptide. Activity of the crude plant extract coincided with the activity of the peptide, indicating that the isolated peptide is mainly responsible for the immunostimulatory activity present in Viscum album extract.