STANDARDIZATION OF DIPHTHERIA ANTITOXIN 8 1 



In a mixture like L 0, the antitoxin has fully neutralized both the toxon 

 as well as the toxin. If, however, more diphtheria poison is added to the 

 I. E., as is done in the L +, the antitoxin, on account of its greater attrac- 

 tion for the toxin, will combine with the latter and leave the toxon free to 

 subsequently carry out its own functions. The more crude poison is 

 added, the more toxon remains unbound, until a point is reached when no 

 more toxin can be taken up and consequently some is leftunneutralized. 

 If the amount of active toxin reaches the dosis letalis minima, it is suffi- 

 cient to kill the animal and thus the limes + is attained. 



When, instead of freshly prepared toxins Ehrlich employed older 

 bouillon cultures, the poisonous qualities distinctly sank to about one-half, 

 but the surprising fact was that the L + had not been altered and even 

 though it had lost one-half of its toxic power, it had still retained its initial 

 activity for neutralizing antitoxin. 



Ehrlich's explanation was . that the diphtheria poison consists of two 

 Toxoid. molecular groups; one the carrier of the toxic qualities, and therefore 

 known as the "toxophore" group, the other uniting with the antitoxin 

 and having the capability of neutralizing it, known as the "haptophore group." The 

 toxophore group is very labile, while the haptophore group, strongly in contrast to it, is 

 characterized by its stability. The toxophore element destroyed, the diphtheria 

 poison loses its toxic qualities, but retains its power to bind antitoxin. A non-poison- 

 ous diphtheria toxin possessing such power is designated by Ehrlich as "Diphtheria 

 Toxoid." 



The mode of standardization of serum advocated at the present day is 

 applicable exclusively to the L + dose. It is effected by injecting guinea- 

 pigs subcutaneously with mixtures of various doses of diphtheria toxin on 

 hand, plus an anti-toxin unit, and noting the smallest amount of toxin 

 which kills the animal in four to five days. This L + as the constant 

 factor is now mixed with different amounts of the serum to be tested and 

 that quantity determined which just prevents the death of the animal. 

 If for example i/ioo c.cm. is necessary, this serum is considered one 

 hundred times as strong as the standard antitoxin unit, or in other words 

 it contains 100 immunity units. 



This method of Ehrlich has been adopted not only in Germany, but almost in all 

 other countries in Europe and also in America. In France the principle varies some- 

 what, as here the serum is tested both for its protective and curative action. The 

 protective power of a serum is considered 50,000 if o.oi c.cm. of a serum saves a guinea- 

 pig weighing 500 gms. from the fatal consequences following a dose of toxin sufficient to 

 kill an animal of the same weight in thirty to forty hours. The standard therefore 

 takes into consideration the relation between the amount of serum and the weight of 

 the animal. The serum is injected into the guinea-pig twelve hours before the toxin 

 and the animal should not lose in weight during the following six days. The curative 

 power is estimated by injecting a guinea-pig with a dose of toxin (sufficient to kill a 

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