DISCUSSION 



Medawar: Brent and Ruszkiewicz, using "mucoid" type extracts 

 (prepared in many cases by Prof. Albert's and Dr. Lejeune's methods) 

 have also found that these extracts inhibit haemagglutination, they do 

 somewhat prolong the life of homografts, but neither of these effects is 

 in any degree specific. What one really wants for this work is something 

 in mice equivalent to the ovarian cyst fluid in human beings, and I 

 wondered if anyone working on transplantation antigens had system- 

 atically screened body fluids of mice to try to find out if any of them 

 contained serologically active substances in a soluble form. The analy- 

 sis of the human blood group substances would not have made anything 

 like its present progress had it not been for Morgan's fortunate dis- 

 covery of the activity of ovarian cyst fluid. 



Davies: There is such a substance in ascitic fluid. It seems to be a 

 dominant agglutinogen of mouse cells, but this is a heat-stable sub- 

 stance, is species-specific, and has no connexion with H-2 antigen; this 

 is Dr. Boyle's "antigen 4". 



Hasek: Demonstration of such a sensitizing substance has been 

 already published by V. Haskova and I. Hflgert (1961. Folia hiol. 

 (Prague), 7, 81). Using the skin-graft test these authors demonstrated 

 sensitizing activity in the cell-free tumour ascitic fluid and in the cyto- 

 plasmic fraction of ascitic tumour cells. 



Davies: Are these materials soluble or do they consist of membrane 

 fragments ? 



Hasek: The originally tested material from cell-free ascitic fluid 

 cannot be described as being in a soluble form, but it was prepared by 

 centrifugation at 18,000-25,000^. 



Medawar: Do these materials contain lipid ? 



Hasek: Yes, they do. 



Davies: The species-specific substance which my colleague Dr. Boyle 

 has isolated does not contain lipid and is soluble. It is present on the 

 surfaces of cells. We immunize rabbits with mouse cells, and this is the 

 dominant agglutinogen. We feel that it is akin to blood group sub- 

 stance. I don't think that it is a membrane fraction, in the sense usually 

 used — that is to say, it is not insoluble. 



36 



