THE AlWEIUIALDEN REACTION 205 



Bronfenbrennor holds tfiat the enzymes exhibit no selectivity, digesting both the 

 antigen and tlie serum impartially.** 



Apparently the digestion is accomplished by serum complement, or at least 

 normal serum enzymes, rather than by any new-formed specific enzyme, although 

 enzymes set free from the tissues have been held responsible by some. 



The mechanism of the reaction is not understood. Jol>ling and Petersen 

 have suggested that the antigen-antibody combination may adsorb or bind the 

 antiproteases of the serum, so that the normal protease digests the serum proteins. 

 Or it niay be that union of antigen and antibody activates the complement, or 

 binds it to the antibodj' so that it digests either the antibody or other proteins 

 of the serum. It also is suggested that enzymes are set free from the tissues 

 injured by the specific protein, or bj' disease, which digest the foreign protein or the 

 cellular proteins that may have escaped from the tissues into the l)lood stream. 



The reaction possesses a certain specificity, but just the degree of this specificity 

 has not been agreed upon. The claim of Abderhalden*^ and his followers, that it is 

 by far the most specific of immunity reactions, whereby disintegration of small 

 amounts of any given organ of an individual can be determined by specific reactions 

 between his serum and that organ, with such refinement that even cerebral localiza- 

 tion is possible,*^ is diflficult to accept. There are so many possible sources of error in 

 the original technic that even with great care the charge of incorrect results from 

 incorrect technic cannot be escaped, and therefore, those who do not accept the 

 doctrine of its specificity are always on the defensive. Nevertheless, so many care- 

 ful and experienced investigators have found the original Abderhalden reaction to 

 give at times absoluteh^ non-specific and hopelessly paradoxical results, that its 

 diagnostic value for either clinical or scientific purposes must be considered at 

 present as unproved,*^ whatever the final decision as to its standing as a specific 

 reaction may be. 



Serum treated with various inert, finelj' divided particles, such as kaolin, starch, 

 silicates, etc., may acquire the property of giving positive reactions. This is 

 another point of resemblance to anaphylatoxin formation, and against the speci- 

 ficity of the reaction, indicating that the antigen merelj^ acts as a non-specific 

 adsorbent. 



By far the most satisfactory results have been recorded in the diagnosis of 

 pregnancy by means of placental antigen. This may be explained by the fact 

 that the protease activity of the serum seems to be increased in pregnancy,*^ and 

 hence the reaction with placenta is more marked than with the serum of non- 

 pregnant individuals. But simply shaking normal serum with kaolin or other 

 foreign substances may cause it to give strong reactions with placenta antigen 

 (Wallis). 



*- Supported by Smith and Cook, Jour. Infect. Dis., 1916 (18), 14. De Waele 

 states that it is the serum globulin that is digested (Compt. Rend. Soc. Biol., 1914 

 (76), 627). 



*' A reply to numerous criticisms is given by Abderhalden, Ferment forschung, 

 1916 (1), 351; this and other numbers of this journal also consist largely of articles 

 on the Abderhalden reaction. 



8^ See Retinger, Arch. Int. Med., 1918 (22), 234. 



*^ O. J. Elsesser (Jour. Infect. Dis., 1916 (19), 655), working in my labora- 

 tory with the purified vegetable proteins of Osborne, found that at best the speci- 

 ficitj' of the reaction was less than that of the anaphylaxis reaction, and there 

 were many absolutely non-specific and irrational reactions. As these pure proteins 

 furnish a much more appropriate material for studying specificity than the tissues 

 or sera commonly used, it would seem that the results thus obtained are excellent 

 proof of the uncertainty and unreliability of the reaction. Careful quantitative 

 studies of the setting free of amino-acids by serum incubated with placenta, 

 by Van Slyke and his associates, also showed a complete lack of specific proteolysis 

 by pregnancv serum (Arch. Int. Med., 1917 (19), 56; Jour. Biol. Chem., 1915 

 (23), 377; see" also Hulton, ibid., 1916 (25), 163). 



«6 See Sloan, .Amer. Jour. Physiol., 1915 (39), 9. 



