INTERRELATIONS 



agents or in some more direct fashion lead to the destruction 

 of the homograft. 



The point of special interest raised by Medawar's specula- 

 tion is in regard to transduction. If multiplying large 

 and medium lymphocytes are specially able to utilize nearly 

 intact pieces of nucleic acid from other cells, the possibility 

 of some type of transduction must exist. On general grounds 

 it would seem that DNA-P, from other cells of the same type 

 multiplying in the immediate neighbourhood, would be the 

 most likely vehicle. This appears to offer an attractive if 

 speculative basis for the transduction that seems to be needed 

 to account for some of the anamnestic phenomena such as 

 those described by Davenport (see chapter v, section 2). 



If a more recent suggestion is correct, and the antigen con- 

 cerned in homograft immunity is of amino-polysaccharide 

 character only adventitiously associated with DNA, most of 

 this discussion will have to be discarded. 



Medawar, like many other authors, believes that the small 

 lymphocyte is an end-cell incapable of diversion. At least 

 an equal number, however, would still allow it potentialities 

 for development. Maximow and Bloom (1948) state that 

 under suitable conditions the small lymphocyte may hyper- 

 trophy and regain the ability to divide. Lymphatic nodules 

 anywhere start from a small focus — conceivably one cell 

 may serve to initiate it — which when first recognizable con- 

 sists of multiplying medium lymphocytes. 



Marshall's description of the initiation of cellular response 

 to antigenic stimuli indicates that small foci of large baso- 

 philic cells appear first in the spleen in the immediate 

 neighbourhood of the arterioles of the pulp and develop 

 mainly to plasma cells. In the Malpighian nodules the first 

 sign is the appearance of mitoses in the centre and the accu- 

 mulation of similar basophil cells which, however, develop 

 further along the lymphocytic path. In lymph nodes the 

 first small foci of plasmablasts appeared in a perivascular 

 situation near the arterioles of the medullary cords. The 



8 113 BC 



