1 62 METHOD OF COMPLEMENT FIXATION 



a period arises during which the antituberculin bodies are so greatly ac- 

 cumulated in the local focus that they ultimately escape into the blood 

 stream. This freely circulating antituberculin neutralizes any freshly 

 injected tuberculin, so that such patients become refractory against even 

 the largest amounts of it. (Tuberculin immunity.) Tuberculin immunity 

 is not, however, in all cases to be identified with a strong antituberculin 

 content in the serum as is demonstrated by the complement fixation 

 method. For example, it is very difficult to produce antituberculin bodies 

 by treatment with S. B. E., although by its use an immunity against B. E. 

 is easily attained. 



The question as to how great a role the antituberculin bodies play, 

 and their exact interpretation is very complicated. The present status 

 of our knowledge may be expressed as follows. 



The administration of the various tuberculin preparations to tubercu- 

 lous patients results in the formation of antibodies within their serum, 

 which with the respective tuberculin as antigen will give the phenomenon 

 of complement fixation in vitro. The different tuberculins are not equally 

 efficient as antigens. Thus B. E. is the best stimulant of antibodies. 

 Furthermore the antibodies obtained from the soluble tuberculin prepa- 

 rations are not identical with those from the insoluble products. Some 

 sera fix complement only with old tuberculin, others react only with new 

 tuberculin. The tuberculous serum of Meyer and Ruppel contains be- 

 sides these two antibodies another group which gives the complement 

 fixation test with an alcoholic extract of tubercle bacilli as antigen (Citron 

 and Klinkert). It may be assumed that with other antigens, other com- 

 plement binding antibodies will be discovered. The presence of these 

 antibodies is of itself no criterion for the existence of a tuberculin 

 immunity. There are tuberculous subjects who are not susceptible to 

 tuberculin and at the same time possess no in vitro demonstrable anti- 

 bodies; reversely, there are very highly susceptible tuberculous individuals 

 with antibodies in their serum. The explanation for the last class of cases 

 has been furnished by Citron. The author demonstrated that the anti- 

 tuberculin contained within the serum in certain instances raises the sus- 

 ceptibility against tuberculin. Thus there is a hypersusceptibility of a 

 humoral form analogous to serum anaphylaxis, besides the hypersensi- 

 tiveness depending upon the increased number of sessile receptors. 



To offer an explanation for the first class of cases (i.e., tuberculous sub- 

 jects with no antituberculin and not susceptible to tuberculin) it has been 

 assumed that besides complement binding agents there are also directly 

 neutralizing or antitoxin-like bodies within the serum. Pickert and Low- 

 enstein could demonstrate that the serum of some tuberculous patients 

 had the property when mixed with tuberculin to so neutralize the latter 



