THEORIES OF ANTIBODY PRODUCTION 



of the Stem cell concerned, so allowing the indefinite 

 production of descendant antibody-producing cells ; 

 (iii) This incorporation of pattern determinants into the 

 genetic structure of antibody-producing cells provided 

 some basis for the changes in antibody character that 

 may result from secondary antigenic stimuli or simple 

 lapse of time. 

 This theory had its main success in predicting that im- 

 munological tolerance following prenatal injection of ap- 

 propriate antigens should be experimentally demonstrable. 

 On the other hand, the concept of self-markers and recogni- 

 tion units was seen to be a clumsy one that could only be 

 a rough paraphrase of the actual mechanism. 



4. Jerne's natural selection theory 



In 1 955 Jerne published a new and strikingly different con- 

 ception of antibody production in which, for the first time 

 since Ehrlich, natural antibodies were seriously considered 

 in relation to 'true' antibodies. Jerne discarded altogether 

 the view that antibody production was a direct result of the 

 entry of an antigen into body cells. He held that the gamma 

 globulin molecules of the plasma represent a population 

 comprising carriers of all the reactive sites needed to unite 

 with any potential antigenic determinant except those already 

 existing in accessible components of the body. The function 

 of the antigen which enters the body from without is to act 

 as ' a selective carrier of spontaneously circulating antibody 

 to a system of cells which can reproduce this antibody'. It is 

 assumed that once antibody is taken into cells of the anti- 

 body-producing system, replicas of this natural antibody 

 will be produced. With the liberation of this crop of new 

 antibody a second injection of antigen will find many more 

 antibody-producing cells and give a stronger 'secondary' 

 stimulus to antibody production. Like the direct template 

 theory, the natural selection theory leaves a considerable 

 range of questions unanswered. It is not clear, for instance, 



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