344 



DISCUSSION 



lethal runting, with almost half of the injected animals having a decrease 

 in their weight curve, while animals injected with normal isologous 

 cells have no decrease in weight. It seems difficult to escape the con- 

 clusion that under these experimental conditions the spleen cell popu- 

 lation of a tolerant animal reacts in a way which is closer to the way in 

 which immunized spleen cells react than to the way normal spleen cells 



Rejection Reaction 



Homologous cells 



Injected 



Fig. I (Voisin). Diagrammatic representation of the proposed hypothesis. 



General scheme : the intensity of the respective reactions (arrows) will lead 



to the possibihties represented in the following figures. 



react. And this seems to me to be extremely important, especially in 

 view of our working hypothesis of recent years which is concerned 

 with the relationships between specific acquired tolerance to hving cells, 

 runt disease and enhancement phenomenon. 



This working hypothesis is diagrammatically represented in Fig. i. 

 When an injection of immunologically competent cells is made intra- 

 venously into a homologous newborn mouse, the subsequent immuno- 

 logical phenomena will evolve in two consecutive phases depending on 

 the state of immunological maturation of the young animal. 



