Preliminary Report on Virus-like Particles in Canine Leukemia and Derived Cell Cultures1

A light and electron microscopic study was made of lymphatic tissues from 2 dogs with reticulum cell leukemia. Virus-like particles were found in both dogs. Cultures of leukemic cells were established from both dogs and 1 culture contained numerous C type virus-like particles. Mycoplasma canis was recovered from the pleural fluid and pleural fluid cell culture of 1 dog. Com parison of this mycoplasma with the virus-like particles showed the former to be more pleomorphic and much larger. M. canis was eliminated from the cell culture and the particles seen in subsequent passages were assumed to be viral rather than a form of mycoplasma.