150 HAEMOLYSIS ISOLYSIN 



of the goat from which it was derived. An obvious explanation 

 would be that the latter did not possess any receptors which it 

 would fit. Another suggestion might be that it had such receptors, 

 but that they were already fully occupied by amboceptors occur- 

 ring in the serum ; but in this case they would attract complement, 

 and solution would ensue. By a method 1 which will not be 

 described here, since it would involve anticipation of facts not 

 yet described, Ehrlich was able to prove the former view the 

 correct one. The immunity, therefore, of the corpuscles of 

 an animal to its own isolysin is due to a complete absence 

 of suitable receptors in its corpuscles, and, we may add, in the 

 entire organism. 



He deduced, therefore, that each blood-corpuscle possesses 

 numerous side-chains with haptophore groups, each of which, 

 when injected into a living animal, is able to combine with a 

 suitable receptor. If we take a particular variety of haptophore, 

 which we will call a, we can see that there are two possibilities 

 after the injection ; it may find no receptors a, in which case 

 there will be no antibody formed, or it may find such receptors. 

 In the latter case there are also two possibilities : there may be 

 receptors a only, or there may be receptors a and haptophore side- 

 chains a. 



If there are only receptors a and no side-chains a, the injection 

 of corpuscles with side-chains a, will lead to an overproduction of 

 receptors a, and amboceptor will be produced. This will act as a 

 haemolysin to the corpuscles injected, but not to those of the 

 animal itself, since they do not contain side-chains to which it can 

 attach itself ; it will be an isolysin, not an autolysin. 



In the second possible case Ehrlich points out that the condi- 

 tions for the production of an autolysin do occur, and such a 

 substance might be produced and might do serious harm to the 

 animal. But it would be produced at first only in small amounts, 

 and the result might be that it would combine with receptor a, 

 which might then be stimulated and cast off and would form anti- 

 ant oly sin. 



1 He first showed that the injection of an amboceptor from one animal into 

 another of a different species would cause the production of an anti-ambo- 

 ceptor, and then showed that the injection of a serum containing isolysin 

 into a goat whose corpuscles it dissolved produced anti-isolysin. These 

 corpuscles contained receptors, since they fixed the isolysin. In the goat 

 from which the isolysin came there was, of course, no production of anti- 

 isolysin. Hence, he argued, it had no suitable receptors in its entire body. 



