I028 TUBERCULIN AND THE TUBERCULIN REACTION 



More recently Selter/ once a champion of the high specificity of the reaction, has 

 come to the conclusion that it is far less specific than is conventionally supposed. He 

 has assembled the evidence for this view/ taking the stand that bacterial infections 

 of a variety of types sensitize the skin and other tissues not only to the specific germ 

 of each infection but to other bacterial proteins as well. For example, he and others 

 have repeatedly seen cross-reactions involving the tubercle bacillus, the colon bacil- 

 lus, the diphtheria bacillus, etc.; and as a consequence he has come to believe that 

 these infections confer an exalted irritability on the tissues rather than specific 

 sensitization. 



This view is probably timely for its renewed warning for caution and less empiri- 

 cism in our interpretation of the tuberculin reaction, but seems to me to exaggerate 

 the importance of the facts observed. In the last analysis it will probably be found 

 that the specificity of the tuberculin reaction lies in its quantitative aspect. The sig- 

 nificant fact is not so much that the tuberculous patient has a heightened sensitive- 

 ness to a variety of foreign, particularly bacterial, proteins, as that he is extraordi- 

 narily sensitive to minute amounts of the active principle of tuberculin. It is not an 

 absolute unspecificity of reaction that is seen, but, as Zinsser and Tamiya^ have well 

 pointed out, a simple overlapping of reaction, such as may be seen throughout the 

 whole field of protein immunological reactions. 



Non-specific reactions in other fields of immunology are discussed by Wells'' who 

 suggests that chemically related proteins as well as identical proteins in different bac- 

 terial and animal bodies may be concerned. In view of the fact that the same amino 

 acid building blocks are common to the large group of proteins, which differ chiefly 

 in the arrangement of these blocks, it is not surprising that non-specific biological 

 reactions, dependent in turn upon chemical similarities, occasionally occur. 



Until we know more of the chemical composition of the proteins of the tubercle 

 bacillus and other bacteria, speculation on this subject will be idle. In view, however, 

 of the great practical importance attached to the tuberculin test in diagnosis, par- 

 ticularly of cattle tuberculosis, the purest preparations of tuberculin available should 

 be used, and in small quantity. In doing this we are taking the greatest precaution 

 possible against the non-specific element. 



RELATION TO OTHER TYPES OF HYPERSENSITIVENESS 



Tuberculin hypersensitiveness is one of the types of change coming appropriately 

 under the broad term "allergy," originally introduced by von Pirquet. This term has 

 been used, however, in so many senses that its significance in the individual case is 

 often not clear, and it is best in the case of the tuberculin type of reaction to follow 

 the self-explanatory if somewhat cumbersome designation "hypersensitiveness of in- 

 fection" used by Coca and Cooke'' for this type of sensitization, manifested in practice 

 by the skin test with bacterial filtrates. 



' Selter, H., and Tancre, E.: Beitr. z. Klin. Tiiberk., 60, 439. 1925. 



^ Selter, H.: Schrijten der Konigshcrger Gelehrten Gcsdlschajl, 2, 137. 1926. 



3 Zinsser, H., and Tamiya, T.: loc. cit. 



'•Wells, H. G.: The Chemical Aspects c,f Immunity. New York, 1925. 



5 Coca, A. F., and Cooke, R. A.: J . Immunol., 8, 163. 1923. 



