LEUKAEMOGENESIS — VIRAL AND CYTOLOGICAL ASPECTS 



71 



as Gross's Passage A virus (see Gross, 1961) in parental and Fj recipients. 

 That the AKR (Gross) virus may enhance the induction of myeloid leukaemia 

 in irradiated RF recipients has been reported by J. Furth (personal communi- 

 cation). The production of both lymphoid and myeloid leukaemias alternately 



Table III. Spontaneous and radiogenic leukaemias in RF, AKR, and F^ 



hybrid mice "f" 



f A. C. Upton, V. K. Jenldns, and J. W. Conklin, unpublished data. 



I Whole-body 250 kVp X-rays administered at a dose-rate of 80-90 r/min. Mice were 

 irradiated at 10 weeks of age. 



by ostensibly the same agent may occur in AKR recipients, depending on 

 whether they are intact or thymectomized (see Gross, 1961). Also in experi- 

 ments with the Moloney (1962) and Graffi (Bielka et al., 1955; Graffi and 

 Gimmy, 1957) viruses, the production of both myeloid and lymphoid 

 leukaemias has been observed. 



The failure of irradiation to increase the incidence of lymphomas in AKR 

 mice or to hasten their appearance conforms to earlier observations (see 

 Upton, 1961). The significance of this failure can now only be guessed at, but 

 viewed in the context of radiation leukaemogenesis it suggests that the 

 "activating" role of radiation is unnecessary in the high-leukaemia AKR 

 mouse, an interpretation consistent with the evidence that active virus is 



