MICE INJECTED WITH ASCITES TUMOUR CELLS 147 



DISCUSSION 



SCOTT: Have you performed some quantitative immunological tests? 

 DKASIL: These are preliminary results. Quantitative tests for DNA synthesis and histo- 

 logical tests are in progress. We have not yet performed any immunological tests. 

 SCOTT: Could I suggest that you might try a very simple test between these two systems? 

 That is pre-immunizing the animals with irradiated cells and then doing quantitative 

 titration of the number of viable cells, which would produce a tumour in a pre-immunized 

 animal. It is a very simple test and you can get a clear-cut answer. 

 BRAZIL: Yes, I agree, we will perform this test in further experiments. 

 KOLLER: One comment on the same question as Dr. Scott has asked about testing 

 quantitatively. Now first of all, what about the strain of mice you used? Did you reduce 

 the dose and give intravenously 10* cells, and did you try and give much less than this, 

 to come down and see at what level the mice react and do not give a tumour at all? In 

 this way I think you can really prove that you are dealing with the suppression of an 

 immune mechanism when you give total-body irradiation. 



drasil: We have performed experiments with different cell numbers in non-irradiated 

 mice only. We studied the dependence of survival on the number of cells injected. We 

 found that when these cells were injected intravenously, after 10* ceUs the survival time 

 increased about 50% and after 10^ cells injected intravenously the survival-time was 

 greater than 120 days. When the cells are injected intraperitoneally, about 10^ to 

 5 X 10^ cells are enough to kill the animal. As to the strain of mice, we used our labora- 

 tory strain H and C57BL. The tumour grows also in C3H and CBA and other strains of 

 mice. 



POCHiN: Was it possible to obtain any evidence as to whether the earlier death was 

 actually due to more rapid tumour growth or could it have been due to other causes? 

 DRASIL: Tliis is a question for further quantitative tests but the post-mortem examina- 

 tions showed that after death these irradiated mice had about the same organ distribu- 

 tion of tumours as the non-irradiated ones.* The size of tumours is at the time of death the 

 same but it seems that tumours in irradiated mice develop faster, and in a greater 

 number, then in non-irradiated mice. 



Note added in proof: Further, more detailed experiments showed an increased 

 percentage of Uver metastases in irradiated animals. 



