The "Lateral-chain Theory" of Immunity 121 



amboceptors have no specific action by themselves, and effect no 

 visible changes when serum containing them is mixed in vitro with 

 the corresponding antigen, for their only function is to form a bond 

 between the antigen and the complement. To determine their 

 presence in any serum or other body juice, it is therefore necessary 

 to supply the complement, when dissolution of the antigen is quickly 

 effected. 



In connection with the factors here involved it is interesting to 

 observe that under certain experimental, and perhaps also under 

 certain natural conditions both amboceptor and complement may give 

 rise to antigenic reactions in the animal body, so that anti-ambocep- 

 tor and anti-complement may be formed. The former, when brought 

 into contact with immune body and antigen, .may substitute itself 

 for the antigen, thus preventing the attachment of the amboceptor 

 to the antigen; the latter may substitute itself for the complement, 

 thus preventing the complement from attaching to the amboceptor, 

 and in either case making impossible the antigen-amboceptor- 

 complement combination by which alone the dissolution of the an- 

 tigen can be effected; 



Such antigens as heterologous red blood corpuscles, spermatozoa, 

 dissociated tissue cells, bodies of micro-organisms destroyed by heat 

 etc., all bring about reactions tending to increase the number of 

 receptors of the third order and occasion the presence of ambo- 

 ceptors in the body juices. 



An analysis of this theory shows complete natural immunity 

 to depend upon the absence of haptophore groups (receptors) by 

 which the toxins can be united to the cells. Extreme sensitivity 

 or susceptibility probably depends upon the adapted haptophores 

 being present or at least most numerous upon the cells of highly 

 vital organs; comparative insensitivity or insusceptibility upon 

 the fact that the greater number of haptophore groups are attached 

 to comparatively unimportant cells whose combining affinities 

 have to be satisfied before combination with more vital cells can 

 be accomphshed. In some cases natural immunity is increased by 

 the presence of free haptophore groups (antitoxin) in the blood. 



Acquired immunity against toxins depends upon the regeneration 

 of the cellular haptophores or receptors which, being liberated into 

 the body juices, fix the haptophores of the toxin molecules before 

 they are able to reach the cells themselves. Antitoxins and other 

 anti-bodies, including the lysins, consist of liberated cellular hapto- 

 phores or receptors, the former having a single combining affinity, 

 the latter a double combining affinity, by which they unite, on the 

 one hand, with the cell to be dissolved, on the other with the com- 

 plement by which it is to be dissolved. Antibodies having this dou- 

 ble combining affinity have been called "amboceptors" by Ehrlich. 

 They are variously known in different writings as "immune bodies," 

 amboceptors, substance sensibilisatrice, desmon, and fixateur. The 



