224 J. R. BATCHELOR AND M. S. SILVERMAN 



tumour growth occurred in the mice receiving sensitized cells; 

 ultimately 5 out of 15 animals succumbed v^hereas in the control 

 group all animals survived v^ith no trace of tumour beyond the 

 third week. There is no doubt that AMT 3 grown in C3H (J is a 

 tumour-host combination particularly favourable for the demon- 

 stration of immunological enhancement, and this must partly 

 account for the observation of adoptively transferred enhancing 

 activity rather than immunity. It is also possible that differences in 

 activity between spleen and lymph node populations might be a 

 subsidiary reason. The pooled immune cell preparations contained 

 a high proportion of spleen cells. Unfortunately the relevant 

 cell counts were not made so that the ratio of spleen cells to lymph 

 node cells is unknovm. But further experiments are in progress to 

 test whether any differences exist between the activity of these 

 two populations. At present another tumour-host combination is 

 also being tested for adoptive transfer of enhancing activity. The 

 prehminary experiments have given inconsistent results, but weak 

 adoptive enhancing activity has been observed in some. 



Prehn (1959) has reported that splenectomy may have an 

 inhibitory effect on the growth of DBA sarcoma 49 transplanted 

 to BALB/c hosts preimmunized intravenously with DBA blood. 

 While investigating the influence which the route of antigen 

 administration may have upon immunization, he found that 

 o-ooi and 0-002 ml. of defibrinated DBA blood given intra- 

 venously to BALB/c mice led to the production of a firm 

 immunity at the 12th day against Sa 49. When the dose of antigen 

 was increased to the equivalent of 0*25 ml. of blood, vigorous 

 tumour growth in excess of that shov^m by the controls resulted. 

 If, however, these animals were subjected to splenectomy, the 

 progressive growth of the subsequently grafted Sa 49 did not 

 occur, and the mice behaved as if immune. It is difficult to 

 explain these observations except on a basis of immunological 

 enhancement. The possibility of immunological paralysis 

 mentioned seems unUkely in view of the antigen dosage and the 



