Leukemia. VIII. Leukemogenic Effect of Brain Filtrates After Serial Passage Through Mice.

Summary 1. Cell-free filtrates of leukemic AKR and Swiss mouse and human brains were prepared. 2. The filtrates were serially passed through Swiss mice in the case of AKR mouse and human brains and through C3Heb mice in the case of Swiss mice. 3. After 5 passages leukemogenic activity could be demonstrated by reintroduction of the material into the starting strain in case of the mice, and into AKR mice in case of human brains. 4. No activity or little activity could be demonstrated when leukemic tissues served as sources of the original material. 5. The experiments demonstrate that the activity of the material is not dependent on cells. 6. The dilution resulting from the passages described is such as to compel the assumption that the activity has been replicated.