CHAPTER IX 



CHEMISTRY OF THE IMMUNITY REACTIONS (Continued)— 



BACTERIOLYSIS, HEMOLYSIS, COMPLEMENT FIXATION, 



AND SERUM CYTOTOXINS 



SERUM BACTERIOLYSISi 



The bactericidal property of serum may be shown by its destruc- 

 tion of the life manifestations of bacteria without marked alteration 

 in their structure, or it may be accompanied by dissolution of the 

 bacterial cell (bacteriolysis). How much of the bacteriotytic process 

 is performed by the serum itself, or how much by the autolytic en- 

 zymes of the bacterial cell, is unknown, but the latter is probably 

 a factor. The bactericidal property of immune serum has been shown 

 to be quite independent of the antitoxic properties and also to have 

 quite a different mechanism. This last is shown in the following 

 manner : 



If we heat bactericidal serum made by immunizing an animal against 

 bacteria, say the cholera vibrio, at 55° for fifteen minutes, it will be 

 found to have lost its power of destroying these organisms. ^ Normal 

 serum of non-immunized animals is equally without effect upon the 

 vibrios. If however, we add to the inactivated heated serum an 

 equal quantity of inactive normal serum, the mixture will be found 

 to be as actively bactericidal as the original unheated immune 

 serum. This phenomenon is interpreted to mean that, by immuniza- 

 tion, some new substance has been developed which, although b}- itself 

 incapable of destroying bacteria, is able, when united with some sub- 

 stance present in normal serum, to destroy bacteria readily. The 

 substance present in normal serum is also incapable of affecting bac- 

 teria by itself, but needs the presence of the substance developed by 

 immunizing to render it bactericidal. Hence the bactericidal prop- 

 erty in this case depends on two siibstances acting together: one, de- 

 veloped during immunization and therefore called the immune body, 

 is specific for the variet}^ of bacteria used in immunization, and is not 

 destroyed by heating at 55°. The other, present in normal serum, is 

 not increased during immunization, is not (altogether) specific in 

 character, and is destroyed by heating at 55°; as its action is com- 



^ Review and bibliography by Miiller, Oppenheimer's Handb. d. Biochcni ., 1909 

 11(0,629. 



^ Normal human serum often exhil)its some jiower to destroy Ijacteria, even after 

 heating to 55°. The nature of this thermostable bactericidal agent is unknown. 

 (See Salter, Zeit. Hyg., 1918 (86), 313). 



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