364 BACTERIOLYSINS 



TECHNIC OF BACTERIOLYTIC TESTS 

 THE PFEIFFER EXPERIMENTS 



The essentials of this important test have been described at the be- 

 ginning of this chapter. Briefly, it consists in making intraperitoneal 

 injections of a bacteriolytic serum mixed with living bacteria into a 

 normal guinea-pig. The resulting bacteriolysis is studied microscopically 

 by withdrawing small amounts of peritoneal exudate at varying inter- 

 vals. By performing the experiment with varying dilutions of serum, 

 the bacteriolytic titer may be determined by noting the dilution in which 

 bacteriolysis just fails to occur in a specified time. 



Pfeiffer also showed that the phenomenon could be produced by in- 

 jecting a mixture of serum from an immunized animal and the culture 

 of cholera into the peritoneum of a normal guinea-pig. This phenome- 

 non appeared when an old specimen of serum was used, as well as when a 

 fresh specimen that had been heated to 60 C. was employed. Later, 

 this observer found that if an old immune serum was injected into the 

 peritoneal cavity and allowed to remain for a time, it regained its bac- 

 tericidal powers. 



Pfeiffer believed that the bacteriolytic substance may exist in the 

 serum of an immunized animal either in an active or in an inert state. 

 In the blood-serum or peritoneal fluid of the living animal it occurs as 

 an active substance, but when kept for a few days or when heated 

 rapidly to 60 C. it becomes inert; it may be rendered active again 

 by coming in contact with the lining endothelial cells of the perito- 

 neum. 



The foregoing constitutes the classic Pfeiffer experiment. The bac- 

 teriolytic amboceptor present in the immune serum is activated by the 

 complement furnished by the guinea-pig. The same serum will not 

 produce bacteriolysis in the test-tube in case it has been heated or the 

 complement is lost through age unless fresh normal serum or peritoneal 

 exudate is added. By immunizing guinea-pigs with gradually increasing 

 doses of cholera serum and then introducing fatal doses of cholera cul- 

 ture intraperitoneally, the same phenomenon of bacteriolysis is observed. 

 In this instance the guinea-pig furnishes both amboceptor and comple- 

 ment. 



By these and similar, experiments and observations Bordet was able 

 to show the role played by the two bodies concerned in cytolysis in 

 general, namely, the thermolabile alexin or complement and the specific 

 sensitizer or bacteriolytic amboceptor. 



