DISCUSSION 21 



Medawar: The possibility of antigens entering the recipient through 

 the intravenous route is something we could perhaps keep in mind 

 when thinking not only of whole organ grafts, established by vascular 

 anastomoses, but also of the relations between the foetus and the 

 mother, between which the traffic is presumably intravenous. As to 

 the inefficiency of the intravenous route generally, there is evidence 

 that this is not a peculiarity of the mouse — it was first described in the 

 rabbit, and there is some evidence also from human beings ; intravenous 

 infusions of living whole blood in human beings, according to Fried- 

 man and his colleagues in Boston (Merrill, J. P., Friedman, E. A., 

 Wilson, R. E. and Marshall, D. C. [1961]. J. din. Invest., 40, 631) do 

 not sensitize, whereas intradermal injections of leucocytes quite certainly 

 do. 



Brent: To complete the catalogue of the situations in which the intra- 

 venous route behaves anomalously, there are the experiments of F. 

 Shapiro and his colleagues. They find that if they inject vast numbers 

 of allogeneic cells (1*5 x 10^) intravenously into adult animals, they can 

 make the animals unresponsive; but the intraperitoneal injection of a 

 similar number of cells apparently does not lead to unresponsiveness. 



Eichwald: How well satisfied are you with your method of assaying 

 survival of skin grafts in terms of percentage ? 



Medaiuar: It is not very good because it is a subjective and rather 

 empirical process. However, Brent and I don't disagree by very much 

 when we score grafts independently. 



Woodruff: Do you think it is likely to be a general rule that the sig- 

 nificant sensitizing antigens in species other than the mouse are the 

 particular ones which also stimulate the formation of haemagglutinins ? 

 In other words, is there a human or rat or rabbit or dog locus with 

 similar properties to the H-2 locus of the mouse ? It seems to me that 

 there is no reason for assuming it at all. 



Barrett: My experience suggests caution in generalizing about these 

 antigens. Some of this emphasis on the H-2 locus is certainly justified 

 on the basis of our information in the mouse. But in my own labora- 

 tory and with my own materials, the properties of the blood (injected 

 from one strain of mouse into another) that will induce dextran-type 

 haemagglutinins and on the other hand those other properties that will 

 produce resistance either against skin grafts or against the implantation 



