ANTIGENS, HAPTENS, ANTIBODIES, ETC. 409 



or no effect . Thus it has been showTi that the determinant 



groups NH^/ }-^-\ /' ™2\ /~™~\ / 



andNHa/ ^— CHg— / y , linked in the usual way to 



proteins, are immunologically equivalent, that is, the 

 antiserum to one will react equally well \sdth any of them 

 as antigen or hapten, the slight differences of field due 

 to the comparatively inert groups — — , — NH — and 

 — CHg — not being sufficient to influence the reactions. 



— C— 

 If, however, the strongly polar group, 1| , replaces the 





 inei-t group, the equivalence is no longer apparent ; 

 antisera to the above antigens will not react with anti- 



gens or haptens containing ^ ^x 



as the determinant group. 



As would be expected from what was said about 

 surface charges in Chapter III, spatial configuration plays 

 an important part in the specificity induced by deter- 

 minant groups. Landsteiner, for instance, coupled the 

 amino -tartranilic acids, which exist in the optically active 

 d- and Z-forms and the optically inactive me5o-form, with 

 proteins and prepared the corresponding antisera. The 

 antisera to the dextro -compound reacted strongly with 

 the cf-antigen, 



OH H 



/ \ I I 



Protein— X =N< >NH.CO.C C"— COOH 



^ ^ I I 



H OH 



Ijut only very slightly with the /-antigen, 



H OH 



Pi-otoin— N -n/ ^NH.CO.C C— COOII 



^ ^ I I 



OH H 



