34 G. LEJEUNE-LEDANT 



actually able to inhibit specifically the agglutination reaction, this 

 inhibition gives us a simple and rapid test for the detection of any 

 transplantation antigen. 



Our experiments show that any antigen which causes a trans- 

 plantation immunity identified by the second-set phenomenon, 

 specifically inhibits the haemagglutination reaction. On the other 

 hand, all the cell-free extracts prepared with the technique used 

 for the preparation of blood group substances, wliich do not cause 

 a transplantation immunity but a prolonged survival of skin 

 homografts of the same donor, inhibit, non-specifically, the 

 haemagglutination reaction. All our complementary assays 

 agree that all the ceU-free extracts producing an inhibition of the 

 haemagglutination reaction, and only these extracts, are able to 

 elicit a transplantation immunity and thus may be considered as 

 transplantation antigens. 



Conclusions 



All homologous cell-free extracts able to induce transplantation 

 immunity also elicit a humoral immunity identified by the forma- 

 tion of haemagglutinins. 



The same extracts inhibit the haemagglutination reaction 

 specifically. 



The results from all our completed experiments and from 

 others now in progress agree that the inhibition of the haemagglu- 

 tination reaction appears to be an accurate and rapid test for the 

 detection of any transplantation antigen. 



Summary 



In mice, homologous isolated cells such as spleen or epidermal 

 cells and homologous tissue extracts from epidermis or spleen 

 cells are capable of ehciting both transplantation immunity as 

 revealed by the second-set reaction phenomenon and humoral 

 immunity as revealed by the appearance of haemagglutinins. 



