TRANSPLANTATION ANTIGENS AND HAEMAGGLUTININS 33 



Discussion 



When we started this experimental work, we were trying to 

 answer the two questions: 



(i) Does antigen sensitizing to a skin homograft of the same 

 donor ehcit the formation of haemagglutinins? 



(2) Is an antigen of tliis kind capable of producing an inhibition 

 of the haemagglutination reaction ? 



As far as the first point is concerned, the problem was far from 

 being solved. Gorer had stressed many times the fact that the 

 A strain is specially favourable for this kind of work. However, 

 Hildemann and Medawar (1959) recently pointed out that if the 

 combination A donor and CBA recipient was indeed serologically 

 the most favourable, the reverse combination CBA donor and 

 A recipient was much less favourable and did not give regularly 

 detectable haemagglutinins. 



A long series of experiments, briefly reported in this paper, 

 demonstrates first that all living cells (especially spleen and epi- 

 dermal cells) capable of inducing transplantation immunity, 

 when injected several times always ehcit the appearance of 

 haemagglutinins in the blood of the recipient. 



Once tliis point was clearly demonstrated for the combination 

 of strains we used, it became much more interesting to verify 

 if the cell-free extracts of those cells had the same properties. 



Once again, the answer is yes, provided that a sufficient anti- 

 genic stimulus is given by repeated injections; the cell-free extracts 

 too elicit the formation of haemagglutinins in the blood of the 

 recipient. The fact that all the antigens — living cells or cell-free 

 extracts — are capable of producing at the same time humoral 

 immunity and transplantation immunity suggests that there must 

 be a very close similarity between antigens forming humoral 

 antibodies and transplantation antigens. 



As far as the second point is concerned, the question is of 

 practical importance: if all the transplantation antigens are 



