150 



INFECTION AND RESISTANCE 



0NTIGEN 

 BACTEZIflLO 

 OTHER CELL 



flflBQCEPTOK 

 ANTIGEN 



& 



SCHEMATIC KEPRESENTATIONS OF A EECEPTOR OF THE THIRD ORDER. 

 Ehrlich 's conception of the relationship of antigen, amboceptor, and complement 

 in the bactericidal and hemolytic process. In A the receptor is still a part 

 of the body cell, in B it has been overproduced, and is free in the circulating 

 blood. 



In his general scheme of diagrammatic representation of these 

 processes Ehrlich refers to the "amboceptors" as "haptines" of the 

 third order. 



Now it is quite plain, from the extreme specificity which results 

 when an animal is immunized with any given variety of blood cells 

 or bacteria, that there must be as great a variety of such amboceptors 

 as there are different antigens, and indeed an animal immunized 

 with two or more antigens may simultaneously contain in its blood 

 serum a corresponding number of different amboceptors. 



This assumption of the multiplicity of a amboceptors" in the 

 same serum is, of coilrse, forced upon us by the fact of specificity, 

 and the frequently repeated observation that the same serum may 

 contain heat-stable lytic antibodies against a variety of antigens, each 

 antigen absorbing out of such a serum that antibody only which 

 specifically reacts with it. This fact has, of course, never been 

 denied, -and it is a frequent misunderstanding of the views of Bor- 

 det, which will be discussed directly, to assume that he has combated 

 the "multiplicity of amboceptor" in the sense just outlined. Ehrlich 

 and Morgenroth, however, have expressed themselves in favor of the 

 conception of a multiplicity of "amboceptor" not only in this sense, 

 but as occurring in response to immunization with one and the 

 same antigen. 



Ehrlich and Morgenroth 37 assume that any cellular antigen, 

 blood or bacterial cell, substances of great complexity of chemical 

 structure, must necessarily be possessed of a large number of differ- 

 ent side chains or receptors. When immunization is practiced with 

 such cells a correspondingly varying number of different ambocep- 

 tors must result. They found, for instance, that when rabbits are 

 37 Ehrlich and Morgenroth. Berl Uin.^Toeh. i Nos. 21 and 22, 1901. 



