Viruses harboured in blasts of the rat myelogenous leukemia (RBA-Le), induced by chicken sarcoma virus.

It was shown that the rat myelogenous leukemia RBA-Le harbours three kinds of viruses. 1. Rat leukemogenic virus, which can be recovered from leukemic cells, medium of cultured leukemic cells and the plasma of leukemic rats. About 12% of rats inoculated when newborn with the recovered virus developed leukemia. 2. Chicken sarcoma virus, which seems to have a lowered infectivity or altered host range as the B77(RBI) virus by which this leukemia had been induced. 3. A cytopathic, hemagglutinating virus, very pathogenic for baby rats, which was shown to be closely related, if not identical in biological as well as immunological properties with Kilham rat virus. The RBA-Le leukemic cells were adapted for growth in tissue culture.