442 THE TECHNIC OF COMPLEMENT-FIXATION REACTIONS 



may be used in conducting any complement-fixation test it is necessary 

 to ascertain its anticomplementary dose, for if this dose were used, a 

 portion of or all the complement would be fixed in a non-specific manner, 

 so that hemolysis, being partial or absent, yields false positive reactions. 



2. Most antigens, when in sufficiently large amounts, are hemolytic, 

 i. e., they may hemolyze corpuscles in a non-specific manner. This 

 hemolytic action is usually due to the presence of undesirable extractives, 

 and extracts of organs that have undergone advanced autolysis or fatty 

 degeneration are known to contain more of these hemolytic substances 

 than do extracts of normal organs. As a general rule, a highly anti- 

 complementary antigen is likely to be correspondingly highly hemolytic. 

 The hemolysis may be due to the presence of lipoidal substances or to 

 the alcohol used in preparing the extract. If an antigen were used in an 

 amount equal to its hemolytic dose, partial or complete hemolysis would 

 occur in all tubes, so that a false negative result would be secured. As 

 a rule, the hemolytic dose of an antigen as determined by titration in 

 the presence of serum is larger than the anticomplementary dose, so that 

 if the latter is known, it is not always necessary to determine the former. 



3. Practically every alcoholic organic extract will serve, in certain 

 amounts, to absorb complement in the presence of the serum of a syphilitic 

 person. Some extracts, however, will do this better than others. The 

 Wassermann .reaction depends upon the fact that a larger amount of 

 complement is fixed by the syphilis antibody and extract than is fixed 

 by normal serum or the serum of a person with some disease other than 

 syphilis and this same extract. The only two notable exceptions to this 

 general rule are to be found with the serum of tuberous leprosy and that 

 of frambesia. The amount of antigen that is found, by a process of 

 titration, to fix a large amount of complement with a constant dose of 

 syphilitic serum is known as its antigenic dose. Not every lipoid serves 

 equally well as antigen, and therefore considerable research work has 

 been done in the hope of discovering an extract or a combination of 

 lipoidal substances that would show a constant reaction and would react 

 only with the syphilis antibody. Thus far this has not been accom- 

 plished; unfortunately, pure pallida antigens are not entirely specific or 

 serviceable, and if the specific and ideal antigen is discovered in the future 

 it will probably be of the nature of a lipoidal substance, altered or pro- 

 duced in a specific manner by the Treponema pallidum itself. In the 

 meantime we have antigens sufficiently delicate and specific, when 

 properly used, to render the Wassermann reaction of great value in the 

 diagnosis of syphilis and to serve as a guide to its treatment. 



