V 



IMPLICATIONS OF THE CLONAL 

 SELECTION HYPOTHESIS 



The preceding chapter contains a general account of the 

 clonal selection hypothesis. In the next three chapters an 

 attempt is made to examine in some detail a rather wide 

 range of immunological topics in terms of the hypothesis. 



The primary objective was, of course, to find situations 

 from which it could be deduced that one or other of the 

 current hypotheses was clearly inadmissible. So far this has 

 proved impossible of accomplishment. 



All experimental work on antibody production has neces- 

 sarily been compelled to employ large natural populations of 

 cells of diverse origins irrespective of whether experiments are 

 carried out in vivo or in vitro. Under these circumstances it 

 seems unlikely that any experimental decision will be possible 

 as between the indirect template hypothesis and the clonal 

 selection hypothesis. It is easily seen that once the capacity 

 to produce antibody has been developed in a cell the implica- 

 tions of the two theories are virtually identical. The difference 

 concerns only the way in which a primary immunization is 

 effected. Is the new pattern produced by a direct impact 

 of antigenic determinant pattern on the protein synthetic 

 mechanism — or does the antigenic pattern act purely as 

 a selective agent on material provided by spontaneous muta- 

 tional processes ? Only by the use of a pure clone technique 

 of tissue culture which allowed mesenchymal cells to retain 

 full functional activity would we be likely to find an answer. 



The clonal selection hypothesis would be completely 

 validated if it could be shown that single cells from a non- 

 immune animal gave rise to clones, each cell of which under 

 proper physiological conditions contained, or could liberate, 



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