Abstract
Summary
1. Passage A leukemic virus, initially isolated from spontaneous Ak mouse leukemia and passed serially through newborn mice, is pathogenic not only for mice, but also for Sprague-Dawley or Osborne-Mendel rats. 2. The virus could be recovered from rats and passed serially in rats. After one or 2 passages in this species, the incidence of leukemia induced in rats following inoculation of this virus increased to almost 100%, and the latency decreased to less than 3 months. 3. In rats the virus induced most frequently lymphatic or stem-cell leukemia, in about 7% also the myeloid form. Lymphosarcomas, and less frequently reticulum-cell sarcomas or Hodgkin's-like lesions, were found in lymph nodes and spleens in some of the leukemic animals. 4. After passage through rats, the virus induced an incidence of leukemia varying from 87 to 97% when inoculated into newborn mice. 5. Thymectomy of rats that had been inoculated with the virus, slightly delayed the development of leukemia: incidence of myeloid leukemia was higher in the thymectomized rats; moreover, one rat in this group developed erythro-myeloid leukemia.
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