42 DISCUSSION 



respond to the tumour and reject it, and the other 90 per cent don't. 

 This suggests, in the first place, that even in animals which do not 

 throw off their tumours, there is a low level immune response which 

 the tumour is able to override by some means or other. Now, if by the 

 injection of red cells, or of red cell stromata, you are eliciting the 

 formation of haemagglutinins and other serum antibodies, could it not 

 be that in this precariously poised system you are producing a syner- 

 gistic effect of the type described by Gorer and Batchelor, so that the 

 presence of the serum antibodies is emphasizing the natural response 

 against the tumour and is just tilting the balance? 



Barrett: In the first place, I don't want to be misunderstood as having 

 said that all antigens are present on the red cell, nor on the other hand, 

 that all red cells of all strains must necessarily give the response that I 

 have got ; all I am saying is that in my system it is there. Secondly, I 

 don't want to be misunderstood, as I have been sometimes, as saying 

 that the white cell is not antigenic in this regard; of course it is antigenic 

 and I suspect that it is more strongly antigenic than the red cell, although 

 I have never put this to the test in my system. Thirdly, in my system, 

 as to the contamination of wliite cells, I was very careful not to make 

 any strong statement about that, but some of you will recall that in this 

 system, when I take all the white cells that can be removed, from ten 

 times the dose that I use for my immunization, these cells only produce 

 half as much effect as do my red cell preparations in which I can find no 

 white cells whatever — though I don't deny that some might get by. 

 Fourthly, as regards the last point that Dr. Brent made: 10 per cent of 

 these animals are on the average resistant to this tumour; however, 

 there are no haemagglutinins generated by any of these procedures, 

 either by multiple inoculations of the tumour, or by ten or fifteen 

 times as much dose of the blood inoculum. 



Nakic: I would like to go back to something Dr. Russell said about 

 irradiating spleen cells and trying to induce tolerance in vitro. Do you 

 think that irradiation might reduce the antigenic power of the spleen 

 cells ? 



Russell: I think it must clearly do so if the dosage is sufficiently high 

 to obviate self-repHcation of the cells of the inoculum. Perhaps what I 

 should do in further experiments is to give repeated doses of irradiated 

 cells because I may have missed tolerance, since it died away before I 



