PRACTICAL APPLICATIONS OF THE COMPLEMENT-FIXATION TEST 155 



Moreschi (at Pfeiffer's institute), while conducting some theoretical studies con- 

 cerning the nature of anticomplements, i.e., such substances which tend to neutralize 

 the action of complements, discovered anew, that by the mixture of a soluble proteid 

 with its antiproteid serum the existing complement disappeared. This, as has been 

 seen, can be explained by the presence within the immune serum of bodies similar to 

 Gengou's amboceptors. Moreschi, however, stated that the complement disappeared 

 because it was thrown to the bottom mechanically, by the occurrence of precipitation. 

 Such a physical explanation for the complement fixation reaction led a number of 

 authorities to the belief that the positive Bordet-Gengou reaction was in reality no 

 amboceptor action, but a result of a similar precipitation process. Wassermann and 

 Bruck, Liefmann, Wassermann and Citron, and later on Moreschi himself realized that 

 this physical explanation was incorrect, inasmuch as complement fixation took place 

 even if all precipitation was prevented by heat or other 'influences. Furthermore, 

 complement binding of an unspecific nature can be produced by the mixture of glycogen 

 or peptone with serum, a procedure wherein surely no precipitation plays any part. 

 Finally Moreschi showed that there were strongly precipitating sera which nevertheless 

 did not exhibit the Bordet-Gengou phenomenon. 



Thus was definitely established that the complement fixation was 

 entirely independent of either bacteriolysis or precipitation. 



Following Moreschi's researches, Neisser and Sachs continued Gengou's 

 studies and advised this demonstration of the proteid amboceptors as a 

 control to the precipitation method for the differentiation of proteids. Its 

 action is so much finer, and more delicate than the precipitin test that even 

 the minutest traces of proteid can be recognized. 



With the encouraging results of Neisser and Sachs in mind, Wassermann 

 attempted by the use of highly immune antibacterial serum to discover 

 any soluble bacterial proteids which may exist in the blood, derived from 

 the respective bacteria invading the organism at the onset of an infection. 

 Practical application proved that not enough of these proteids existed free 

 in the circulation, but that they were probably bound by the tissue cells. 



Wassermann and Bruck then employed the complement fixation test 



with the idea of demonstrating the existence of the respective antigens in 



the diseased organs. Tuberculous glands and lungs served as material for 



this experiment. They were able to obtain complement fixation when an 



extract of tuberculous organs as antigen was mixed with a tuberculous 



serum (manufactured by the Hochst Farbwerke) . If instead of the latter, 



the ' serum from tuberculous individuals was substituted, no positive 



complement fixation reaction was obtained. On the other hand, the 



reaction was given if the human tuberculous serum employed 



Antituber- came from an individual who had received therapeutic inocu- 



culin. lations of tuberculin. In other words, the serum of treated 

 individuals contained, in contrast to the untreated ones, 

 amboceptors against a soluble tuberculous substance also present in the 

 extract of tuberculous glands. Wassermann and Bruck identified this 

 substance as tuberculin, because the sera of the treated individuals gave 

 the same positive results if a solution of old or new tuberculin was used in- 



