232 PASSIVE IMMUNIZATION 



vocated by Bail and his school, is the lack of its antiaggressin action. This 

 applies only to the cases in which the bacteriolytic serum was produced by 

 immunization with dead bacteria. 



When live bacteria are used, this objection is not to be considered, as 

 according to the experiments of Wassermann and Citron, "aggressin" is 

 nothing more than the immunizing substance of the living bacteria. As 

 far as the structure of the antiaggressins is concerned, the author was 

 able to show that like the bacteriolysins, they are amboceptors which 

 bind complement. 



Artificial aqueous extracts of living bacteria, belonging to the class of 

 half parasites made according to the method of Wassermann and Citron, 

 contain the endotoxin as well as the aggressin. Such artificial aggressins, 

 therefore, represent ideal antigens. The sera produced by their injection 

 contain but few bacteriolytic bodies and a very large number of ambo- 

 ceptors, easily demonstrable by the Bordet-Gengoa reaction. 



Wassermann explains the lack of therapeutic efficiency on the part of 

 the bacteriolytic sera by the absence of complement of the organisms, as 

 well as by the inability of human complement invariably to fit animal 

 amboceptors. As is known, amboceptors increase during immunization 

 while the complement content remains the same. But since amboceptors 

 without complement remain inactive, even a very strong serum may only 

 be slightly effective, depending upon the amount of existing complement. 

 If too many amboceptors are injected, the serum may become entirely 

 powerless due to a phenomenon similar to Neisser and Wechsberg's 

 complement deviation. Wassermann advises therefore the addition of 

 complement to a serum before its injection, in order to activate it. This 

 suggestion has not been widely adopted in practice. 



It is for a similar reason, that the classical experiment of bacteriolysis 

 is so beautifully demonstrable in the guinea-pig's peritoneal cavity, an 

 area relatively poor in cells, while this phenomenon is incomplete and 

 replaced by phagocytosis when occurring in the blood, inner organs, and 

 subcutaneous connective tissue. It is in this connection that Metch- 

 nikoff and his followers see the main reason for the failure of the therapeutic 

 activity of bacteriolytic sera. 



An additional impediment is offered by the wide differences which 

 exist among the numerous strains of the same bacterium. This may be 

 so marked that an immune serum produced with one strain will offer no 

 protection against a different strain of the same bacterium. It is now 

 overcome to a certain extent by immunization with as many different 

 strains of the same bacterium as possible (polyvalent sera). 



Cultures grown upon artificial media for a very long time adapt them- 

 selves to their new surroundings and frequently lose some of their bio- 

 logical characteristics, e.g., virulence. If the culture is then inoculated 



