490 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



for an hour, 1 per cent, glycerin and 0.5 phenol are added as preservatives, 

 and the mixture stored away in ampules containing 1 c.c. each. The 

 emulsion should be slightly milky in appearance. 



The antigen is diluted 1 : 10 or 1 : 20, and the anticomplementary 

 dose determined by titration before the main tests are conducted. The 

 technic of the reaction is exactly similar to the gonococcus fixation test. 



The ease with which the Widal reaction is performed renders it the 

 method of choice. Nevertheless the complement-fixation test is quite 

 delicate, and will frequently aid, where the agglutination test is negative 

 or absent and in making the differential diagnosis from paratyphoid 

 fever. The strongest reactions are secured late in the disease. 



COMPLEMENT-FIXATION TEST IN TUBERCULOSIS 



It was the original studies in complement fixation in tuberculosis 

 made by Wassermann and Bruch that later induced these workers, in 

 cooperation with Neisser, to apply the method to the diagnosis of syphilis. 



Antigens were prepared of tuberculous glands and lungs, and com- 

 plement fixation was found to occur with an artificial immune serum 

 (Hochst) and with the serums of persons who had received injections of 

 tuberculin, but not the serums of other tuberculous persons who had 

 not received tuberculin. 



It would appear, therefore, that tuberculin may stimulate the pro- 

 duction of tuberculin antibodies in the nature of amboceptors (Citron). 

 These amboceptors will frequently fix complement in vitro with a suitable 

 tuberculin antigen. 



According to Citron, a tuberculous focus may contain tuberculin, 

 and antituberculin is probably produced by healthy cells in or about the 

 focus, which are capable of reaction. The production of antituberculin, 

 however, is a transitory process, arising only when tuberculin has reached 

 the circulation, either spontaneously or artificially. During this stage 

 the serum of the patient may yield a positive complement-fixation test. 

 Following this stage of activity there comes a period of quiescence dur- 

 ing which no free antituberculin can be demonstrated in the blood-serum. 

 The cells, however, are sensitized, and possess many sessile receptors 

 that possess a high affinity for tuberculin and produce antituberculin 

 much more readily than do normal cells. Hence when a small amount 

 of tuberculin is injected it is bound by the sensitized cells in the zone 

 surrounding the tuberculous focus, and thus explains the heightened 

 action at this point, with the production of antituberculin. 



