Pathogenic Properties,and “Vertical” ∗ Transmission of the Mouse Leukemia Agent. †

Abstract

Summary

1. When centrifugated extracts of Ak mouse leukemia were inoculated into 16 suckling C3H(f) infant mice less than 12 hours old, “spontaneous” leukemia developed in 8 of them at 81/2 to 11 months, and in 5 mice at 14 to 18 months of age. 2. When the centrifugated leukemic extracts were inoculated into 20 C3H(f) infant mice 3 to 6 days old, “spontaneous” leukemia developed in 10 of them, but not before they were 18 months of age. 3. Filtered (Seitz) leukemic extracts were inoculated, in 2 experiments, into 7 C3H(f) infant mice 8 days old, and 2 of them developed leukemia at 23 and 27 months respectively. In 5 additional experiments, leukemic filtrates were inoculated into 25 C3H(f) infant mice less than 12 hours old, and 7 of them developed “spontaneous” leukemia at 61/2 to 9 months of age. These results suggest that the Ak mouse leukemia agent is filterable. 4. In 5 experiments, suckling infant C3H or C3H(f) mice were inoculated with either centrifugated leukemic extracts, leukemic cell suspensions, or with normal Ak-embryo-cell suspensions. After the inoculated infant mice have grown up and reached sexual maturity, they were mated, Of the 10 inoculated parents, 7 eventually developed “spontaneous” leukemia at 9 to 19 months of age. Of the 27 untreated offspring, 13, or 48%, have thus far developed “spontaneous” leukemia at 14 to 20 months of age. The results of these experiments suggest that the mouse leukemia agent is transmitted from parents to their offspring. The transmission of the agent occurs most probably directly through the embryos(2,4). 5. The incidence of spontaneous leukemia among the untreated males and females of the C3H or C3H(f) colonies of mice in our laboratory has been, during the past several years, less than 0.07%.