Immunological mechanism of action of the tumor reducing peptide from mistletoe extract (NSC 635089) cellular proliferation.

A peptide isolated from the Viscum album extract (Iscador) has been reported earlier to the both cytotoxic and tumour reducing. Spleen cells from animals treated with a very small quantity of this peptide were found to have increased response to phytohaemagglutinin and Concanavalin-A, indicating that more mature lymphocytes are produced by the peptide administration. Moreover injection of the peptide at the lesion site produced infiltration of lymphocytes and macrophages and finally producing necrosis of the tumor. This peptide also stimulated macrophages in vitro and in vivo and activated macrophages were found to have cytotoxic activity towards L-929 fibroblasts.