TRANSPLANTATION TOLERANCE AND AGE 



143 



I 3 



c 



0-2 



0-1 



00 



— I — 

 64 



62 64 66 6-8 70 72 74 

 Log. dose administered to infant (A xC57BL)F| hybrids 



O , • = standard and test suspensions for assay of mouse no. 1295 

 □ , ■ = standard and test suspensions for assay of mouse no.1306 

 Fig. 2. Results of assays of the type illustrated in Fig. i. Spleen 



index = 



spleen weight 



of mouse receiving S or T suspension 



body weight 

 spleen weight 

 body weight 



the graph represents an average of two litters. (Data from Michie 

 and Woodruff, 1962.) 



of mouse receiving B suspension. Each point on 



Adoptive ittitnunization 



Enhancement was earlier listed as a possible interpretation of 

 specific unresponsiveness to skin grafts induced by earlier workers 

 in adult mice. This possibility is not formally excluded in our own 

 case. We have, however, been able to narrow the field somewhat 

 by testing for the presence in our graft-bearing mice of an 

 "efferent block", by virtue of which the graft might be enabled 

 to survive in face of a rejection reaction on the part of the host. 

 In such a case, the graft would be unaffected by adoptive immunity 

 conferred by injection of isologous lymphoid cells preimmunized 

 against the skin-donor. If, however, no efferent block exists, as in 

 the case of tolerance, the same procedure would result in rejection 

 of the skin graft. 



