204 CHEMISTRY OF THE IMMUNITY REACTIONS 



doubtful. The processes involved in hay fever are characteristically of the nature 

 ■ of an anaphylactic reaction to a foreign protein, in which case we cannot speak of 

 either a toxin or an antitoxic senim. The hypersensitization seems sometimes 

 to be established spontaneously throusrh inheritance, but no antibodies can be 

 demonstrated in the blood of sensitized persons, although the cells of the skin 

 and mucous membranes are reactive,"' so that the specific protein responsible for 

 the trouble may be determined by skin or conjunctival tests. Essentially, there- 

 fore, hay fever is one of the cases of hypersensitivity to foreign protein, of the same 

 class as horse asthma, food urticarias, etc. 



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, Friedemann, Friedberger and others. It 

 differs from the other reactions of this class merely in that tlie methods used for 

 determining the proteolysis are chemical rather than biological. The occurrence 

 of a reaction is indicated by the production of diffu.sible products of protein hy- 

 drolysis, which may be detected by any one of several methods, although most 

 used is "ninhydrin" (triketohydrindene hydrate)'* which 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 peptone 

 under the hydrolytic action of the serum. 



It has undergone much the same series of shifting explanations as the other 

 reactions of this class. At first, like the other proteolytic reactions, it was assumed 

 that the antigen was digested; but, as with the precipitin and anaphylaxis reac- 

 tions, evidence was found by numerous observers that not the antigen but the 

 proteins of the immune serum are the chief or sole source of the cleavage products. 

 For some reason, hard to explain, it has always been referred to as if it were the 

 result of the formation of specific enzymes which attacked the antigen, in spite 

 of the repeated demonstration that sera giving positive reactions can be inacti- 

 vated by heat and reactivated by normal serum, '^ thus throwing it into the class 

 of amboceptor-complement reactions, with which it agrees in principle. 



Having been introduced first as a method for diagnosing pregnancy, on the 

 principle that in pregnancy the chorionic cells of the placenta enter the maternal 

 circulation and as foreign proteins cause the formation of specific "defensive fer- 

 ments," it was at once taken up as a clinical procedure, and as a result an enormous 

 literature on this reaction was rapidly produced. Much of this represents highly 

 uncritical work, largely from workers not trained or experienced in immunological 

 principles, and hence it is not profitable to review it in extenso here. Abderhalden's 

 own views are given in full in his monographs^" and there exist numerous critical 

 reviews.^' The status of the reaction at this writing seems to be as follows: 



Animals, or man, after having foreign proteins of any sort enter the blood 

 stream, may, and commonly do show an altered condition of their serum, whereby 

 when their serum is incubated with the antigen under suitalile conditions very 

 minute quantities of the products of protein cleavage may be set free, and recog- 

 nized when dialyzed away from the digesting mixture; or, a measuralile change in 

 optical rotation of the digestion mixture occurs. However, jierfectly normal 

 sera may at times cause a similar proteolysis, usually but not always less thaji with 

 the immune serum. 



The digestion seems to involve chiefly the serum jiroteins rather than the anti- 

 gen, although under certain conditions there may he some digestion of the antigen. 



" See Cooke, Flood and Coca, Jour. Immunol.. 1917 (2), 217 



'* Concerning the mechanism of the ninhydrin reaction see Retinger, Jour. 



Amer. Chem. Soc, 1917 (39), 1059. 



'9 See Stephan, Mlinoh. med. Woch., "1914,1(61), 801; Ilauptman ibid., p. 1107; 



Bettencourt and Monezes, Compt. Rend. Soc. l^iol., 191() (77), 102. 

 *" Emil Al)der]ialdcn, "Schutzfermcnte des tierischen (_)rgaiusmus." 

 81 See Wallis, Ouart. Jour. Med., 1910 (9), 13S; Bronfenbrenner, Jour. Lab. 



Clin. Med., 1915 (1), 79; 1910 (1), 573. Hulton, Jour. Biol. Chem., 1910 (25), 



103. 



