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



necessary to employ a particularly favourable strain and sex 

 combination. The duration of antigenic stimulus to which cells 

 are subjected is an important variable, as Mitchison emphasized. 

 He noted evidence of adoptive immunity following transfer 

 of lymph nodes taken 3-5 days after the implantation of the 

 immunizing tumour graft (Sa i). Billingham, Brent and 

 Medawar (1954) took nodes at 11 days from animals sensitized 

 by allogeneic skin. Although immunity can be detected with 

 regularity after 4 days' apphcation of alien skin (Berrian and 

 McKhann, 1959) when tested by means of further skin grafts on 

 the same host, in our experience the activity of adoptively trans- 

 ferred draining lymph node cells from BALB/c c? hosts grafted 

 bilaterally with C3H skin is weak at the 5th day, judged by 

 tumour inhibition but of marked potency by the nth day. By 

 the 5 th day after multiple-site immunization with neoplastic 

 tissue sensitized cells of obvious activity can be otained. But it is 

 possible that the type of immunological activity may be influenced 

 by this method of sensitization. During this work it has been 

 assumed that such lymph nodes, known to contain sensitized cells 

 but presumed not to be at their peak of humoral antibody syn- 

 thesis, are the most suitable for synergic experiments. If endo- 

 genous humoral antibody synthesis is proceeding at such a rate 

 as to cause a surplus in excess of that absorbed by the graft, 

 further serum injected by the experimentahst is unhkely to 

 provide a factor essential for graft destruction. 



The initial experiments were performed on C3H mice grafted 

 with A-strain skin. The hosts were injected intraperitoneally with 

 pooled spleen and lymph node cells sensitized against an A-strain 

 mammary tumour homogenate (AMT 3), and challenged with 

 A-strain skin grafts on the same day. No evidence of adoptive 

 immunity was observed even when 165 million pooled lymph 

 node and spleen cells were administered. The cell-treated animals 

 frequently showed shght prolongation of skin survival times, and 

 it was considered possible that these might represent enhancement. 



