On the mode of action of heterologous antileukemic sera. Growth of syngeneically transplanted leukemias in serum-treated sublethally irradiated mice (author's transl)]

Heterologous antisera against mouse leukemias prevented the outgrowth of syngeneically transplanted leukemia cells only in non irradiated but not in sublethally irradiated animals. Mice irradiated with 500 R and controls were subcutaneously injected with 50000 leukemia cells at the day following irradiation. They were given 5 injections each of 0,1 ml of heterologous antiserum. Whilst 22 out of 27 irradiated mice developed tumors non-irradiated controls were protected, only 2 out of 30 animals developed a tumor. Cytotoxicity tests with leukemia cells as targets and mouse serum as complement source showed that the complement activity of mouse serum had not been suppressed by the whole body irradiation. We suppose a cooperation between heterologous antiserum and a radiosensitive host cell as responsible for the antileukemic effect.