Serial Cell-Free Passage of a Radiation-Activated Mouse Leukemia Agent.

A filterable leukemic agent designated “virus X'recovered from a C3H female in which leukemia was induced by x-ray irradiation, was passed serially through 4 consecutive cell-free inoculations of suckling C3H mice. 2. Of 40 mice inoculated, 26 thus far developed leukemia (65%) at ages varying from 3 to 11 months. 3. Inactivated (56°C 1/2 hr) rabbit and guinea pig serum, prepared with agent X filtrates, only partially neutralized passage A leukemic agent; passage A immune rabbit serum had a distinct, though not complete neutralization effect on the passage A agent.