18 INTRODUCTION TO IMMUNOCHEMICAL SPECIFICITY 



antigen system, it is usually found that the homologous hapten in- 

 hibits best and that other haptens inhibit more or less well, depend- 

 ing on the degree of their resemblance to the hapten contained in the 

 immunizing antigen. Thus, in Table 2-1 we see that mononitro- 

 strychnine inhibits the reaction of an anti-strychnine antiserum with 

 a conjugated strychnine-antigen as well as does strychnine itself, 

 whereas the related alkaloid brucine, which differs from strychnine 



TABLE 2-1 



Inhibition of Anti-Strychnine Sera by Various Haptens* 

 Hooker and Boyd, 1940 



» Hooker and Boyd, 1940. 



*> The symbols indicate the degree of precipitation obtained when the hapten- 

 serum mixture was overlayered with a suitable concentration of the strychnine- 

 protein antigen. The symbol + indicates a positive precipitation reaction, ± a 

 weak reaction, "t" a faint trace, and no precipitation. Absence of a symbol 

 means that the test was not done or could not be read because of nonspecific 

 precipitation. 



only in possessing two methoxy groups, does not inhibit as well ; that 

 is, a larger amount of it is required to prevent the antibody-antigen re- 

 action. The unrelated alkaloid morphine does not inhibit at all. In 

 this case the effectiveness of different haptens was compared by 

 testing decreasing amounts (increasing dilutions) of the haptens 

 against a constant amount of antiserum, to which was later added a 

 suitable amount of antigen. 



In general, we may expect the results obtained with haptens H, H', 

 H", and G, where H' is closely related chemically to H, W less 



