234 DISCUSSION 



of isoantibody you may have some afferent blocking effect; but I think 

 also that antibody is capable of interfering with activated immune cells. 



This question of which direction your immune response takes is very 

 peculiar. Why should you get one type of response rather than the 

 other? For example, in the allergic encephalomyehtis story, why 

 should a single inoculation with normal brain tissue unmixed with 

 adjuvant set your immune apparatus in a direction so that you don't 

 subsequently respond with allergic encephalomyehtis ? 



Barrett: Dr. Batchelor referred to Dr. R. T. Prehn's work on dosage 

 and route of antigen administration and said that he thought the results 

 should be explained on the basis of immunological enhancement rather 

 than paralysis. I would like to reinforce this. Dr. Prehn and I did many 

 of our experiments with the same materials at the same time. With my 

 methods of immunization, but with the same materials, I have used 20 

 times that dose and seen only the standard immunity, so I feel confident 

 that that dose is not only not paralysing but it isn't even close to being 

 paralysing. 



Dr. Prehn used a shghtly different technique from the one I used, but 

 with the same animals and the same tumours. His inocula were always 

 intracutaneous and it was only under these circumstances that this en- 

 hancement was seen. Equal doses of all other materials would give 

 immunity if the transplants were subcutaneous, and the slight differ- 

 ences which occur between Dr. Prehn's and my work are due to 

 differences in the dosages and differences between the subcutaneous and 

 the intracutaneous sites. This tumour, as has been remarked previously 

 in this meeting, will kill 90 per cent of B ALB/c animals when inoculated 

 in small doses subcutaneously, but when inoculated in small doses 

 intracutaneously it will regress in all animals. The balances are quite 

 dehcate. 



Feldman: I am in favour of any theory of enhancement which does 

 not imply a blocking of the afferent direction of antigens. Our experi- 

 ments on passively-induced enhancement showed that enhanced 

 tumours, while growing progressively in the foreign host, do elicit a 

 high degree of transplantation immunity, which could be demonstrated 

 by passive transfer of the lymph node cells. Several possibilities can be 

 raised to explain this, such as (i) the coating of the tumour cells by 

 humoral antibodies, thus protecting the cells from the cytotoxic effect 



