l80 DISCUSSION 



E. Klein: You mean that the homotransplanted tumours have lost 

 some antigen ? 



Feldman: Apparently, but this is not manifested in their susceptibility 

 to transplantation immunity. 



Lawrence: Could it be that with the hapten induction of the tumour 

 you have covered the H-2 antigens, and in so doing have altered the 

 "selfness" of that individual mouse by your hapten complex? This 

 could cover the reactive groupings of what would be the H-2 agglutin- 

 in, and therefore interfere with induction of antibody formation, but 

 not with the abihty to absorb it. This has some particular bearing in 

 view of Cell and Benacerraf's (1961. J. exp. Med., II3, 571) recent 

 findings (which had been postulated for homologous tissue antigens by 

 Mitchison) that if simple chemicals are coupled to an individual's own 

 serum constituents this manoeuvre will alter the selfness of such 

 materials. Cell and Benacerraf have shown that with simple chemical 

 (picryl or p-chlorobenzoyl group) complexing of a guinea pig's own 

 or other's serum albumin, for instance, it then functions as a foreign 

 antigen for that host. I wonder how much of tliis sort of alteration may 

 be contributing to the anomalous behaviour of your tumour homograft. 



Feldman : Any of these possibilities might have happened. But since 

 we do not know the antigenic structure of these antigens, it is hard to 

 devise an experimental system to answer this question directly. 



Loutit: When we injected sarcoma I, which is an A-strain tumour, 

 into CBA/A radiation chimeras it produced (i) a little tumour, and (2) 

 enormous enlargement of the lymph glands and spleen, a tremendous 

 metastasis, so that superficially the animal appeared to have lympho- 

 matosis. I understand that Dr. Feldman's chimeras where foetal tissue 

 has been given for restoration look the same. In our CBA mice given 

 adult A bone marrow, the lymphoid tissue was completely replaced by 

 hyaline fibrinoid material; the animals virtually lost their central 

 mechanism of lymphoid tissue. If our CBA hosts are given foetal liver 

 for restoration, we see a similar histological picture — complete absence 

 of lymphoid tissue and a splenic pulp consisting of myeloid tissue. 

 Dr. Feldman, you have discussed the afferent system and the efferent 

 system. Have you any evidence of what is happening in the central 

 system ; is the lymphoid tissue intact ? 



Feldman : No, I haven't. We did not really follow the morphological 



