Antigen Action. 49 



guished by groups, which make possible their combining with cer- 

 tain groups of the cell substances of the body. The "haptophore" 

 groups of antigens under certain conditions fit as a key fits the 

 lock, into the haptophore group of the "receptors," thus making 

 possible the binding of the antigens to the cell. These terms were 

 applied to these bodies by Ehrlich. 



The simplest way of explaining the mechanism of the antigen 

 action and the anti-body formation is by using toxin as an example. 



A toxin is an antigen with a haptophore binding group, and a 

 poison-producing group, the toxophores. If the toxin enters the 

 body of an animal it may find groups on the cell to which it fits, 

 the so-called receptors, which bind its haptophore group. If this 

 has been the case the toxophore group exerts its action, the effect 

 of the toxin becomes noticeable and the animal suffers as a result 

 of the toxin. If there are no receptors present for the specific 

 toxin it is impossible for the toxin group to exert its action, and 

 the animal is therefore resistant against this respective toxin. 



It is possible that as a result of the receptors of the cell com- 

 bining with the toxin, the cell molecule is destroyed. But if the 

 damage is not too serious, the protoplasm is stimulated to produce 

 numerous receptors, an over-production in fact. As not all of 

 these are necessary for the performance of the cell function, the 

 superfluous ones are rapidly thrown off into the body fluids. If 

 such free receptors combine with the haptophore groups of the 

 toxin, the latter is no longer able to combine with the protoplasm 

 of the cell. These free receptors therefore protect the body against 

 renewed action of the toxin, that is they act as antitoxins, and con- 

 stitute the antitoxic part of the serum. 



Besides the antitoxins, the action of which lies principally in 

 the neutralization of the binding group of the toxin (anti-bodies of 

 the first order), there are still more complicated receptors, for 

 instance those which possess an active or ferment-producing 

 group ; they are anti-bodies of the second order. Finally there are 

 anti-bodies of the third order, which are unable to act by them- 

 selves, but must utilize a third body in order to exert an action on 

 the antigen. 



Immune bodies of the third order become complete in their 

 action only through the utilization of the complement. These im- 

 mune bodies of the third order possesss therefore a binding group 

 for anchoring the antigen, and a binding group for the complement. 

 They are amboceptors, in contradistinction to the uniceptors of the 

 first and second order. 



Some anti-bodies resist heating for a half hour at 56 deg. C. ; 

 they are thermostabile, as for instance the antitoxins, the agglu- 

 tinins, the amboceptors, while others, as for instance the comple- 

 ment, are destroyed at this temperature, as they are thermo-labile. 



Tf, for instance, hemolytic anti-bodies are produced in a rabbit by treating the 

 rabbit with red-blood corpuscles of another animal, then the hemolytic rabbit serum 

 lo^es its action by heating to 56 de^. C. 



