ANTITUMOROUS AND IMMUNOMODULATORY EFFECTS OF THE VISCUM-ALBUM L PREPARATION ISOREL

There are numerous data on the immunostimulative and antitumorous acti vity of various Viscum album tissue extracts. Isorel (Novipharm, Austr ia) is one of these compounds. We found that in mice an increased numb er of plaque-forming cells to sheep red blood cells (SRBC) followed th e injection of Isorel together with SRBC. Further, survival time of a foreign skin graft was shortened if Isorel was applied at the correct time. Finally, suppressed immune reactivity in tumorous mice recovered following Isorel injection. Isorel was further shown to be cytotoxic to tumor cells in vitro. Its application to tumor-bearing mice could p rolong their life but without any therapeutic effect. However, a combi nation of local irradiation and Isorel was very effective: following 4 3 Gy of local irradiation to a transplanted methylcholanthrene-induced fibrosarcoma (volume about 240 mm3) growing in syngeneic CBA/HZgr mic e, the tumor disappeared in about 25% of the animals; the addition of Isorel increased the incidence of cured animals to over 65%. The combi ned action of Isorel, influencing tumor viability on the one hand and the host's immune reactivity on the other, seems to be favorable for i ts antitumor action in vivo.