CHROMOSOMES IN MURINE PRE-LEUKAEMIA 



87 



Table II. Mice of thymic weight more than 70 mg 



Transplantation of pre-leukaemic tissue 



As well as the cytogenetic scoring, observations of the transplantability of 

 various tissues from the pre-leukaemic animals were made according to the 

 following plan. 



1. Portions of the thymus were transplanted into less than 24-hour-old 

 mice. C57BL as well as C6 thymuses were transplanted into the C6 hybrid to 

 make use of the marker chromosome should malignancy subsequently appear. 



2. Thymuses of C6 animals were also transplanted into less than 40-day- 

 old C6 mice thymectomized withm the preceding 24 hours. 



3. In the case of the C6, C57BL mice were lethaUy irradiated and resusci- 

 tated with bone-marrow from the pre-leul^aemic C6 and portions of its 

 thymus, spleen and lymph node were transplanted into these chimaeras. In 

 the case of the C57BL, C6 mice were lethally irradiated and resuscitated with 

 bone-marrow from the pre-leukaemic C57BL and portions of its thymus, 

 spleen and lymph gland were transplanted into the resultant chimaeras. 



All were kept as test animals for 1 year and then sacrificed. 



No animal transplanted with pre-leukaemic tissues as in 1 or 2 developed 

 transplantation malignancy and no abnormality was detected at post-mortem. 

 In contrast four out of the five overt leukaemias shown in Table II proved their 

 autonomy by transplanting. Where radiation chimaeras were utilized for 

 transplantation tests, all tests were negative with the exception of the pre- 

 leukaemic mouse sacrificed 119 days after the last irradiation; this exception 

 is now reported in detail. 



