68 



ARTHUR C. UPTON 



leukaemia and also with Down's syndrome in which the probability of leuka- 

 emia is increased. These developments and their implications call for re- 

 evaluation of radiation leukaemogenesis in the light of viral and cytological 

 factors. 



KOLE OF VIRUSES 



The viral aetiology of fowl leukosis was established more than 50 years 

 ago, but efforts to demonstrate this cause in mammalian leukaemia were 

 unsuccessful until Gross proved the extraordinary susceptibility of newborn 

 mice to cell-free leukaemogenic agents (see Gross, 1961). Since this discovery, 

 an increasingly large and diverse series of filterable leukaemogenic agents has 

 been found (Table I) and it has been observed that leukaemias induced by 



Table I. Mouse leukaemia viruses f 



Origin 



Neoplastic cell 



Investigators 



AKR, C58 (spontaneous lymphoma) 



C3H (radiation lymphoma) 



C57BL (radiation lymphoma) 



BALB/c (sarcoma 37) 



BALB/c (C3H plasma cell neoplasm) , 



Swiss, C3H (spontaneous lymphoma) 



Swiss (Ehrlich carcinoma) 



BALB/c (EhrUch carcinoma) 



Sarcoma I, Sarcoma II, SOV 16, Ehrlich 

 carcinoma. Sarcoma 37 



RF/Up (radiation myeloid) 

 Friend virus 



Lymphoid 



Lymphoid 

 (sarcoma) 



Reticulum cell 



Gross (19.51, 1956) 



Gross (1958, 1959) 



Lieberman and Kaplan (1959) 



Moloney (1960) 



Breyere and Moloney (see 



Moloney, 1962) 

 Schoolman et al. (1957) 

 Schwartz et al. (1959) 



Friend (1957) 

 (erythroblastosis) 

 Reticulum cell, Stansley et al. (1961) 



type B 

 Myeloid Graffi et al. (See Graffi, 1958; 



Moloney, 1962) 



Myeloid Upton (1959) 



Lymphoid Rauscher (1962) 



(erythroblastosis) 

 Myeloid (?) Mirand and Grace (1962) 



t Modified from Moloney (1962). 



radiation in low leukaemia strain mice (C3H (Gross, 1958, 1959), C57BL 

 (Lieberman and Kaplan, 1959), and EF (Upton, 1959; Parsons et al., 1962)) 

 yield filterable leukaemogenic agents. So it has been inferred that this 

 induction probably involves some form of virus activation. 



Studies of radiation-induced myeloid leukaemia were carried out with 

 mice of the RF strain, in which the incidence of this disease may be increased 

 from the control level of about 3% by only 150 r of whole-body X-radiation 

 (Upton, 1959). Although the presence of viral leukaemogenic agents in affected 



