IMPLICATIONS OF CLONAL SELECTION 



evolving population as subject to mutation and selective 

 survival in all their complications as any large animal popu- 

 lation in nature. The initial population may be determined, 

 say, at the beginning of immunological maturity by the 

 stabilization of wholly random patterns from which those 

 reacting with body determinants have been withdrawn. With 

 the first impact of infection, however, the clonal pattern will 

 be altered, first by simple selective survival and subsequently 

 by the combination of somatic mutation and survival. As in 

 every other evolutionary situation, the occurrence of neutral 

 or deleterious mutations is quite unimportant, no matter how 

 frequently it occurs. It is only the mutant which finds its 

 opportunity to proliferate when the appropriate antigen is 

 in the internal environment that is significant in changing 

 the balance of the mesenchymal clones within the body. 



In many ways the effect of adjuvants seems likely to pro- 

 vide an important field for comparison of the implications of 

 template and selection theories. It could be said, for instance, 

 that on any template hypothesis, if an animal can produce 

 antibody as a result of the use of adjuvants, it should also be 

 capable of doing so without adjuvants. To account for the facts 

 on this hypothesis it seems that we must wait until a mutant 

 clone of cells appears which differs from the normal in being 

 able to incorporate the template and produce antibody. This 

 is virtually to accept most of the clonal selection hypothesis. 



Another line of thought might be that the presence of the 

 adjuvant materials attracts a local accumulation of pre- 

 dominantly monocytic cells. Antigen taken into these cells 

 is converted, according to one elaboration of template theory, 

 into a form which can be taken as template into a cell of the 

 lymphocyte-plasma cell series. It could be argued that the 

 much larger number of monocytes which could have ex- 

 perience of the antigen would increase the chance that some 

 of it was converted into the necessary modified form. It 

 should not be difficult to find experimental situations to 

 differentiate these possibilities. 



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