CHAPTER VIII 



CHEMISTRY OF THE IMMUNITY REACTIONS (Con- 

 tinued)— BACTERIOLYSIS, HEMOLYSIS, COMPLE- 

 MENT FIXATION, AND SERUM CYTOTOXINS 



SERUM BACTERIOLYSIS ' 



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 bacteriolytic process 

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

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

 a factor. The bactericidal property of immune seriTm has been sho^^^l 

 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 w^e 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 by 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 hactericidal prop- 

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

 veloped during immunization and therefore caHed the inintioie hody, 

 is specific for the variety 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 eom- 

 plementar}' to that of tlie specific innnune body, it is called the com- 

 plement.^ 



1 Review and liiljlio^rrapliv l)v ^Vfiiller, Oppeiilieimer's TTaiull). d. Bioelicm., 1009 

 (II (1) ), 629. 

 - 'J'lie i)olyiiuc]ear Icucocyies also coniain l)actoriolytic agents, "endolysins," of 



210 



