CHAPTER XXII 



THE BASIS OF BACTERIAL COMPLEMENT 

 FIXATION TECHNIQUE 



Introduction. -Ill the pi-ecediiig' chapters the subjects of 

 aiilijieus, antibodies and coiuplenicut liavc been discussed along 

 witli our i>resent concepts of spccificit.y, cellular sensitization and 

 the binding of complement by sensitized cells. It remained for 

 Bordet and Gengou (1901) to discover that one could ascertain 

 Avhether a given sample of serum contained antibodies for a specific 

 bacterial antigen by mixing the two together with complement 

 and later testing with sensitized red cells to see whether the comple- 

 ment had been bound. If the serum under investigation contained 

 antibodies for the bacterial antigen, one would expect sensitization 

 of the bacterial cells and a subsequent binding of complement. 

 One could determine whether complement was bound or free by 

 adding sensitized red cells, incubating and examining for hemol- 

 ysis. Bordet and Gengou saw at once that such a procedure 

 might be helpful in tlie diagnosis of certain specific infectious dis- 

 eases to ascertain the kind of antibodies in the blood stream. They 

 also realized that by this means an unknown organism might be 

 identified as accurately as by the agglutination test. In the 

 present chapter it is proposed to discuss the methods of perform- 

 ing the test and call attention to the reasons for adopting certain 

 standard procedures. 



The Original Bordet-Gengou Technique. — The original comple- 

 ment fixation technique was introduced by Bordet and Gengou 

 in 1901 and can best be understood by a study of the accompanying 

 protocol from their paper (Table X). These tubes were incubated 

 for five hours at 15-20° C, and to each tube was added 0.2 c.c. of 

 sensitized rabbit blood cells, and the tubes were shaken and in- 

 cubated at 37° C, for one hour, when the results were read 

 and recorded. The tubes appear as in Plate V. 



It was found that in Tube A no hemolysis occurred after the 

 sensitized red cells were added. The reason is presumably that 

 the anti-pestis serum sensitized the bacteria in the pestis emulsion 



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