226 



J. R. BATCHELOR AND M. S. SILVERMAN 



of interest that this effect is more easily obtained in BALB/c cJ 

 than in$, a finding similar to the demonstration of enhancement 

 following passive immunization v^ith isoantibody. 



It may be worth while now to recall some of the known facts 

 bearing upon immunological enhancement. Theoretically this 

 phenomenon may result from a modification of the grafted tissue 

 or of the host reaction, or of both. Evidence upon modification 



Fig. 3. Influence of splenectomy in BALB/c (^ hosts 

 grafted subcutaneously with BP 8. 



splenectomy 



sham operation 



Tumour size is plotted as average diameter in mm. 



of each group of 5 animals. BP 8 inoculum=5-4 



million cells. 



of the graft is incomplete. KaHss (1958) has recorded that en- 

 hanced tumours transplanted to further incompatible hosts may 

 retain their characteristic pattern of progressive growth over 

 several transplant generations. Although Snell and co-workers 

 (i960) have recently failed to observe similar behaviour in another 

 test system, the positive results of Kaliss cannot be ignored. It is 

 unknown, however, whether humoral antibody absorbed upon 

 the transferred tumour cells would be sufficient to perpetuate the 

 conditions leading to enhancement. Kahss (1958) rejected the 



