The Viscum album (mistletoe) preparation
Isorel is able to destroy tumour cells and to modify immune reactivity against a particular
antigen in normal and in tumour-bearing animals. CBA/HZgr mice and
methylcholanthrene-induced
fibrosarcoma were used in these studies. A single dose of
Isorel M (140 mg/kg or 1400 mg/kg
body weight) significantly increased the number of plaque forming cells if applied at the time of injection of sheep red blood cells or 1 day earlier. The application of
Isorel 1 day after sheep red blood cells did not modify the number of plaque forming cells in comparison to the controls. The higher the dose of
Isorel the stronger is the immune response to sheep red blood cells. Furthermore, one dose of
Isorel (140 mg/kg
body weight) restored the suppressed immune response of
fibrosarcoma-bearing mice to a significant extent. Besides modification of the humoral immune response, the survival time of C57BI/GoZgr male skin grafts on syngeneic female recipients was significantly shorter if
Isorel was applied at a particular time after grafting. However, according to plaque forming cell numbers, a prolonged application of
Isorel was significantly immunosuppressive in normal mice and particularly in tumour-bearing mice. It should be mentioned that the doses of
Isorel used in this experiment were much higher than generally used in
cancer patients. In view of the immunomodulating effects of
Isorel, the monitoring of the immune response of the patients treated with mistletoe preparations is to be recommended.