140 THE METHOD OF COMPLEMENT FIXATION. 



if the plurality of complement exists, the hemolytic complement should 

 still be present. Accordingly, after a certain interval, washed erythrocytes 

 and inactivated homologous immune serum were added and 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 bac- 

 teriolytic but also the hemolytic complement. Bordet and Gengou there- 

 upon 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 among other things that absorption 

 of complement was not always 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 com- 

 plement. Antigen alone, or even amboceptor alone, cannot or perhaps only very slightly 

 bind the complement. Whether the zymotoxic (energy) group of the complement 

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

 different for the complement fixation. 



Through complement fixation, as introduced by Bordet and 

 Complement Gengou, one * s ena bled 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 of serum diagnosis can be widely employed, as the majority of 

 Diagnosis, bacteria and immune 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 



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



