BORDET AND GENGOU PHENOMENON 153 



hemolysis looked for. No hemolysis took place, thereby attesting to the 

 fact that the bacteria in the first part of the test had "fixed" ("held in 

 check") not only the bacteriolytic but also the hemolytic complement. 

 Bordet and Gengou thereupon named this test "complement fixation" or 

 "complement binding" (La fixation d'alexine). 



With the aid of this experiment Bordet and Gengou were able to prove a number of 

 theoretically important points. They demonstrated that absorption of complement 

 was not necessarily accompanied by bacteriolysis. For example, the anthrax and 

 pest bacteria when mixed with their respective homologous immune sera show no 

 or only very incomplete bacteriolysis. The erroneous conclusion thus reached, to 

 the effect that these sera contained no amboceptors, was disproved by Bordet and 

 Gengou, who demonstrated that, i, these sera contained amboceptors in spite of the 

 absence of bacteriolysis, 2, the complement was absorbed, although no bacteriolysis 

 took place. 



During the process of immunization, amboceptors were found far more frequently 

 than bacteriolysins. These two terms must not be considered as synonymous. 



Amboceptor signifies a more generic term, and one must differentiate between amboceptors 

 of cytolytic and non-lytic properties. Whether the difference here really depends upon 

 the different nature of the amboceptor, or upon the construction and constitution of 

 the antigen, is not solved. 



The fixation of the complement precedes the act of bacteriolysis. The important 

 requirement for the fixation is an antigen which has been sensitized by the attachment 

 of the amboceptor* thus increasing the affinity toward the haptophore group of the 

 complement. Antigen alone, or even amboceptor alone, binds the complement only 

 very slightly or not at all. Whether the zymotoxic (energy) group of the comple- 

 ment manifests its activity (bacteriolysis) or not (absence of bacteriolysis) is materially 

 indifferent for the complement fixation. 



Through complement fixation, as introduced by Bordet and 

 Complement Gengou, one is enabled to prove the presence of specific anti- 

 Fixation as bodies when the antigen is known or reversely, an unknown 

 a Method antigen provided the specific antibody is given. This method 

 of Serum o f serum diagnosis can be widely employed, as the majority of 

 Diagnosis. Dac ^ er i a an( j i mmune sera (with the exception of pure antitoxic 

 sera) 1 when mixed homologously, give a positive reaction 

 the absence of hemolysis, proving the absorption of complement by the 

 union of the antigen and its specific amboceptor. This reaction is strongly 

 specific. If bacteria are mixed with an inactive heterologous immune 

 serum, or with a heated normal one, not in concentrated form (normal 

 amboceptor), and complement is added, the latter will not be fixed but 

 remains to be taken up by the subsequently added red blood cells, and its 

 immune serum, causing hemolysis. Hemolysis indicates that the mixed 

 bacteria and serum are not homologous, as the complement is left free, and 

 given a chance to unite with the added erythrocytes and hemolytic ambo- 

 ceptor. In the case where the bacteria are known, e.g., typhoid bacilli, 

 the occurrence of hemolysis indicates that the examined serum contains no 



1 Even antitoxic sera are said by Nicolle to give complement fixation reactions. 



