IMPLICATIONS OF CLONAL SELECTION 



concentration of inducer which would be ineffective in 

 producing the primary (permease) effect and therefore in- 

 duce no /?-galactosidase production by the unmodified strain 

 (Novick and Weiner, 1957). 



There is nothing to suggest that any detailed resemblance 

 to the adaptive enzyme situation is involved, but one can 

 readily imagine that once a genetically ' competent ' mesen- 

 chymal cell is stimulated specifically by antigen, a trans- 

 missible (? cytoplasmic) condition might be induced which 

 would allow more direct activation of the descendants to 

 proliferate and produce antibody. 



2. Anamnestic responses 



There is a good deal of confusion in the Hterature in regard 

 to whether any stimulus other than specific antigen can 

 provoke a rise in antibody titre in an animal previously 

 immunized with that antigen. There is much to be said for 

 the view expressed by Fischel, Lemay and Kabat (1949) that 

 if a single antigen, in their case crystalline ovalbumin, is 

 used, no antibody rise is produced by steroid hormones or 

 other non-specific stimuli. 



They did not, however, carry out the more interesting 

 experiment of seeing to what extent related antigens, for 

 example, fowl serum albumin, duck ovalbumin and bovine 

 serum albumin, could provoke a secondary rise and whether 

 that rise was due to antibody reacting preferentially with the 

 first or with the second antigen. This was subsequently done 

 by Dixon and Maurer (1954) and their results will be 

 discussed later. 



This topic is one of the greatest importance for any clonal 

 approach to antibody production. In the application of any 

 such theory, it will be necessary to know : 



(i) the size and complexity of the average antigenic deter- 

 minant, which will be defined as the portion of the 

 antigen complementary to a given reactive site on an 

 antibody molecule, 



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