TRANSPLANTATION ANTIGENS AND HAEM AGGLUTININS 3I 



the recipients were challenged with a skin homograft of the same 

 donor, they showed regularly an actual prolongation of the 

 survival of their grafts. This phenomenon is not, however, 

 entirely specific and may be obtained in some cases with isologous 

 extracts. It seemed worth while to test in parallel the action of 

 various cell-free extracts, including the latest ones, on the 

 haemagglutination reaction. 



Haemagglutination inhibition method 



Hyperimmune serum SA anti-CBA is diluted in dextran 

 solution at I • 8 per cent in three series of tubes. In all the series, the 

 first two tubes are used as controls and contain only a 2 per cent 

 red cell suspension and the dextran solution. In the other tubes of 

 each series, hyperimmune serum is diluted at various concentra- 

 tions: i/i, 1/40, i/ioo, 1/200, i/iooo. 



The first series gives the titre of the haemagglutinins. 



The second series contains the hyperimmune serum SA anti- 

 CBA and the homologous extract CBA in contact for 30 minutes 

 at 4°. After this incubation, red cell suspensions in 50 per cent 

 v/v absorbed human serum are added. The haemagglutination 

 reaction is read after 60 minutes' incubation at 37°. 



The third series of tubes is prepared in the same manner, but 

 contains the isologous SA extracts. 



For the reaction to be specific, inhibition of the haemagglutina- 

 tion must be positive only with the homologous CBA extract. 



Results 



Our results are summarized in the Tables III and IV. 



All cell-free extracts, whatever the kind of extraction technique, 

 which cause the production of transplantation immunity in the 

 recipient, detected by a second-set phenomenon when challenged 

 with a skin homograft of the same donor, all such extracts 

 produce a specific inhibition of the haemagglutination reaction. 

 Indeed, there is no inhibition when isologous extracts are used. 



