COMPLEMENT FIXAT/(>.\ liKM'TlOS 229 



COMPLEMENT FIXATION"' AND WASSERMANN REACTIONS'' 



The original principle involved in these reactions was first demon- 

 strated by Bordet and Gengoii, and is essentially as follows: If a 

 specific antigen and amboceptor unite in the presence of complement, 

 the complement is then united to the amboceptor-antigen compound 

 to complete the reaction. When sufficient amounts of amboceptor 

 and antigen are present the entire quantity of available complement 

 may be thus fixed, and, consequently, the mixture contains no more 

 complement for further reactions. As complement does not ordinarily 

 unite with amboceptors except when the amboceptors are united with 

 their specific antigens the fact that in a given system of 



complement + amboceptor + antigen 

 \ 

 there is no free complement, is evidence of a reaction between ambocep- 

 tor and antigen; in consequence of which this reaction can be used to 

 determine the presence of a specific amboceptor in a serum^ by using 

 the corresponding antigen; or conversely, with a scrum containing a 

 known amboceptor we can detect the presence in a solution of the 

 specific antigen. The indicator of the presence or absence of comple- 

 ment which is in universal use, is the ability of the mixture to hemolyze 

 erythrocytes in the presence of the specific hemolytic amboceptor. 

 Thus, if typhoid bacilli and a typhoid antiserum which contains both 

 complement and specific amboceptor, are mixed in proper proportions 

 and incubated for a short time, the complement will be bound to the 

 bacilli. If we then add this mixture to sheep corpuscles which have 

 been acted upon by an antisheep-corpuscle serum, from which the 

 complement had been previously removed by heating, no hemoh'sis 

 will occur, for we have added no free complement. But if our original 

 mixture had contained dysentery bacilli instead of typhoid bacilli 

 the complement would not have been fixed, and the addition of this 

 mixture, containing free complement, to the sensitized sheep corpuscles 

 would cause prompt hemolysis. 



This reaction was at first used for the detection of antibodies in 



■•^ The reaction of ''complement fixation" must not be confused with the eu- 

 tirelj' distinct reaction of ''complement deviation," a mistake very likely to ha])pen 

 because of the careless but erroneous use by some writers of the latter term in 

 describing the first-named reaction. Complement deviation (or Neisser-Wechs- 

 berg phenomenon) is produced when an excess of amboceptors is present together 

 with antigen and a limited amount of complement, which results in absence of 

 complement activitv. The mechanism of this reaction lias not been satisfactorily 

 explained. Thjotta (Norsk. Mag. Laegevid., 1919 (80), 1051) believes it to de- 

 pend on some special substance, distinct from the known antibodies, which adsorbs 

 complement. 



■"Literature given by Meier, Jahresbor. d. Immunitatsforsch., 1909 (4), 58; 

 Sachs and Altmann, Kolle and Wassermann's Handbuch, Ergiinzungsbd.. 2, 1909, 

 p. 476; Noguchi, "Serum Diagnosis of Svphilis and Luetin Reaction,"" I'hiladel- 

 phia, 1912. 



