Studies on the Role of Virus in the Development of Leukemia by X-ray-iradiation Report Ⅱ. Electromicroscopic Demonstration of Virus Particles in the X-ray Induced RF Mouse Leukemia

Electromicroscopic studies on the lymph nodes of RF mice with X-ray induced leukemia revealed in intercellular spaces round virus particles, 100 mμ in average diameter, each consisting of an outer membrane and a nucleoid body. They belong to C type virus particles according to the classification of oncogenic viruses by Bernhard, et al or Hiraki, et al. The virus particles showed an identical morphology and process of formation with those of spontaneous leukemic virus. This present report combined with successful implantation of cell-free filtrate from leukemic mice reported in the previous paper gives firmer ground to the idea that inactive virus latent in normal RF mice through vertical transmission was activated by X-ray to act on normal cells to transform into leukemic cells.