Pathogenic Properties, and "Vertical" Transmission of the Mouse Leukemia Agent.

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Abstract
When centrifuged (3000 rpm. for 30 min.) 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 8.5-11 months of age, and in 5 mice at 14-18 months. When the centrifuged 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. Filtered (Seitz) leukemic extracts were inoculated, in 2 expts., into 7 C3H(f) infant mice 8 days old, and 2 of them developed leukemia at 23 and 27 months,respectively. In 5 additional expts., leukemic filtrates were inoculated into 25 C3H(f) infant mice less than 12 hrs. old, and 7 of them developed "spontaneous" leukemia at 6.5 - 9 mos. of age. These results suggest that the Ak mouse leukemia agent is filterable. That this agent is transmitted from parents to offspring was demonstrated in 5 expts. in which suckling infant C3H or C3H(f) mice were inoculated with either centrifugated leukemic extracts, with leukemic cell suspensions, or with normal Ak embryo cell suspensions. After the inoculated infant mice grew up and reached sexual maturity, they were mated. Of the 10 inoculated parents, 7 eventually developed "spontaneous" leukemia at 9-19 mos. of age. Of the 27 untreated offspring, 13 or 48%, have thus far developed, and died from, "spontaneous" leukemia at 14 to 20 mos. of age. The results of these expts. suggest that the mouse leukemia agent is transmitted from one generation to another. This transmission occurs most probably directly through the embryos (Gross, Proc. Soc. Exptl. Biol. and Med. 76: 27-32. 1951). 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%.