204 CHEMISTRY o/' THE fMMCX/TY REACTIONf? 



elusively that anaphylactic shock is induced by reaction between an- 

 chored antibody and antigen, and tliat circulating antibody plays abso- 

 lutely no role in its production." 



The anaphylactin shows quite the same characteristics of specificity 

 as the other immune antibodies,"' in that proteins of closely related 

 species tend to interact, while proteins of \ery distinct biological or 

 chemical nature are easily distinguished. Thus, guinea-pigs sensitized 

 with ape serum will react with human serum, but not with serum 

 from dog or ox or fowl. However, in the final analysis, the speci- 

 ficity depends upon the chemical composition of the antigenic protein, 

 rather than its biological origin, for I have found it possible to dis- 

 tinguish in the hen's egg five distinctly different antigens, and these 

 correspond to five proteins which have been distinguished by chemical 

 measures. Together with Dr. T. B. Osborne, working with purified 

 vegetable proteins, I have found evidence that a single isolated protein 

 (hordein or gliadin) may contain more than one antigenic radical. ^^ 

 As Osborne ^^ has said, "chemically identical proteins apparently do 

 not occur in animals and plants of different species, unless thej' are 

 biologically very closely related." Whether the chemical differences 

 that determine specificity are of quantitative nature, which can be 

 disclosed by analytic means, or whether they are sometimes dependent 

 upon spatial relationships of the amino-acid radicals, as Pick sug- 

 gests, remains to be determined. ]\Iy own experience indicates that 

 usually, at least, proteins distinguishable by anaphylactic reactions 

 also show readily distinguishable chemical differences. 



THE ABDERHALDEN REACTION 



This reaction is based upon ,the hypothesis that the animal body 

 reacts to the presence of foreign proteins by providing specific means 

 of destroying them through proteolysis, and hence is fundamentally 

 the same as the anaphylaxis reaction as conceived by Vaughan, Friede- 

 mann, Friedberger and others. It differs from the other reactions of 

 this class merely in that the metliods used for determining the proteo- 

 lysis are chemical rather than biological. The occurrence of a reac- 

 tion is indicated by the production of diffusible products of protein 

 hydrolysis, which may be detected by any one of several methods, 

 altliough most used is "ninhydrin" (triketohydrindene hydrate) 

 wiiich reacts with any alpha-amino acid, the resulting condensation 

 compound being a blue or violet color, or by observing the change in 

 optical rotation that occurs in a solution of i)eptone under the hydro- 

 lytic action of the serum. 



It has undergone nnich llie same scries of shifting explanations as 

 the other reactions of tliis ehiss. At first, like the other proteolytic 



;" See review in Jour. Tnfoet. Dis.. 191 1 (S). 7:?. 

 a«.T()ur. In fee. Dis.. 1013 (12), 341. 

 3'JHarvev Leetures, 1010 11. 



