XL. THE MECHANISM OF THE ACTION OF 

 ANTIAMBOCEPTORS. 1 



By Prof. PAUL EHRLICH and Dr. H. SACHS. 



OWING to closer investigations into the nature of immunity our 

 conceptions regarding the relation between antibody and the sub- 

 stances exciting the production of immunity (the antigen, as it is 

 called) have undergone a certain modification. This consists in a 

 more precise definition of the concept specificity. In the beginning 

 it was assumed that an antibody produced by immunization acted 

 only against the substance through which it was developed. Further 

 observations, however, soon brought to light cases in which this 

 law was apparently violated. A clear insight into this subject was 

 finally made possible when the receptor was looked upon as the 

 agent which excited the production of immunity. According to 

 the side-chain theory, therefore, specificity of the antibodies always 

 means " the specific relations between the individual types of antibodies 

 and of receptors." 2 Since, therefore, the same receptor can be dis- 

 tributed not only among different kinds of cells, and bodies of differ- 

 ent functions all within the same animal species, but also among 

 different species of animals, we see that it is impossible to speak of 

 a specificity in a zoological sense, or of a specificity in respect to the 

 morphological or functional properties of the antigens. The anti- 

 body is specific only for the receptor, i.e., for those elements possess- 

 ing this fitting receptor. 



Of the various substances which excite the production of im- 

 munity, a special place is occupied by the receptors of the third order: 

 these, when free, constitute the amboceptors. As is well known, 

 the amboceptors possess a double function. On the one hand they 

 unite with the cytophile group of the cells, and on the other with the 



1 Reprinted from Berliner klin. Wochenschrift, 1905, No. 19. 



2 P. Ehrlich and Morgenroth, Haemolysins. See page 88. 



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