130 PRACTICAL METHODS IN IMMUNITY. 



FIXATION OR ABSORPTION OF THE COMPLEMENT. 



One of the controversies in connection with the nature of the 

 complement is that regarding the question of the unity of complements 

 or whether there exist different kinds of complements for different 

 amboceptors (unity and multiplicity of complement). To prove that 

 a single complement will act with varying amboceptors, Bordet and 

 Gengou showed that the same complement would activate both 

 haemolytic and bacteriolytic immune bodies. If to a mixture of 

 typhoid bacteria and inactivated typhoid immune serum some 

 guinea pig serum is added and the mixture be allowed to remain at 

 37 C. for 2 hours, and then sensitized red cells be added and the mix- 

 ture again be placed in the incubator for 2 hours, no haemolysis will be 

 found to have occurred, because the bacteria have absorbed all the 

 guinea-pig complement through the intervening typhoid amboceptors, 

 and there is no complement left to haemolyze the red cells through the 

 specific blood-cell amboceptors. If, instead of immune typhoid serum, 

 the serum of a normal person had been used, there would have been 

 no amboceptors to unite the complement to the bacterial cells. The 

 complement would then be at hand to unite with the sensitized red cells 

 subsequently added and bring about their haemolysis, as shown by the 

 ruby color of the supernatant fluid. This phenomenon of Bordet and 

 Gengou has been utilized by Wasserman for the diagnosis of diseases 

 where cultures are not applicable. It is in the diagnosis of syphilis 

 that it is best known. It at present being impossible to obtain cultures 

 of Treponema pallidum, we use emulsions of the liver of a syphilitic 

 foetus, which have been filtered so as to be clear, instead of a culture. 

 The syphilitic liver, as can be observed by staining according to 

 Levaditi's method, is packed with spirochaetes. 



For the immune bodies we take the serum of the patient, or if a case 

 of locomotor ataxia or general paresis, the cerebrospinal fluid. This 

 is heated to 56 C. to destroy complement (inactivation). For the 

 complement we use normal guinea-pig serum in a dilution of i-io. 

 For the sensitized cells we use the cells of some animal whose defibri- 

 nated blood has been used to immunize a second animal, as human 

 blood injected into rabbits. Consequently, as for haemolysis experi- 



