154 



METHOD OF COMPLEMENT FIXATION 



typhoid amboceptors. If the serum is known (e.g., meningococcus serum) 

 the occurrence of hemolysis proves that the bacteria under examination 

 are not meningococci. The absence of hemolysis will in the first case 

 point out that the unknown serum contains typhoid amboceptors, i.e., is 

 a typhoid serum; while in the second case the absence of hemolysis would 

 bear definite evidence in favor of meningococci. The accompanying 

 figures, 15 and 16, represent schematically the positive and negative 

 complement fixation test. 



Typhoid bacilli (antigen) 



Typhoid 



Inactive typhoid serum (typhoid am- 

 boceptor) 



I Typhoid 



Complement amboceptor 



Hemolysin (hemolytic amboceptor) 



Sheep's red blood cells (2d antigen) 

 Result: Due to the union of comple- Complement 

 ment with the complex typhoid bacillus 

 -f- the typhoid amboceptor, hemolysis 

 does not take place. 



FIG. 15. 



Typhoid 

 bacilli 



Typhoid bacilli (antigen) 



Inactive cholera serum (cholera ambo- 

 ceptor) 



Complement 



I Cholera 



Hemolysin amboceptor 



Sheep's red blood cells 

 Result: The complement unites with 

 the hemolysin and the sheep's red blood 

 cells thus producing hemolysis. 



FIG. 16. 



V7 Red blood cell 



VI 



Hemolytic 

 amboceptor 



Complement 



Gengou further showed that not only cellular antigens can stimulate 

 the formation of amboceptors, but that during the course of immunization 

 with proteids in solution (milk, serum, etc.), complement binding ambo- 

 ceptors are also formed in addition to the precipitins. Citron has there- 

 fore proposed the term " antigenophile," to designate the "cytophile" 

 group of the amboceptor. 



Widal and Lesourd were the first to make practical application of the 

 complement fixation property. They found that the Bordet-Gengou re- 

 action could be obtained far more frequently and earlier with the serum of 

 typhoid patients than the agglutination test. Nevertheless, this entire 

 complement fixation method remained unheeded for several years. 



