322 GUY A. VOISIN AND RADSLAV KINSKY 



These are precisely the three orders of results which can be 

 experimentally obtained by passive enhancement of the newborn: 

 retardation, attenuation or suppression of runting. Furthermore, 

 the weight curves of the survivors of the two series of animals 

 (protected and not protected) are extremely close, almost identical 

 (except for a slight but constantly higher level of the curve for the 

 protected animals) and, at the same time, they are much lower 

 than the curve of the normal, non-injected control group. This is 

 taken as a suggestion that the survivors, in the two groups, were 

 submitted to analogous modifications, that is to say that the 

 mechanism by which the survivors of the unprotected group 

 overcame runting was probably analogous to the mechanism by 

 which the treated animals were protected. Had the two mechan- 

 isms been different, one would have expected a difference to be 

 observed some time during the evolution, either in weight or in 

 another symptom. This proved not to be the case. It seems then 

 both likely and reasonable to think that the facilitation reaction 

 is the usual operative mechanism which protects newborns 

 injected at birth with homologous cells against runting. 



What then are the implications of this enhancing action of 

 specific sera in newborn mice ? 



II. Immunological facilitation (enhancement phenomenon) 

 applied to non-tumour tissues 



A. Passive enhancement of non-tumour tissues 



This work seems to be the first unequivocal passive transfer of 

 immunological enhancement toward non-tumour tissue. In 

 order to follow the development of the reactions and to visualize 

 the identity between this experimental situation and the situation in 

 enhancement of tumour homografts, one has to stop thinking in 

 terms of donor and recipient and to think in terms of immuno- 

 logically competent partner (the recipient of the tumour homo- 

 graft or the splenic cells injected in the newborn) and immuno- 



