Chapter I 



Blood Groups, Heterogenetic (Forssman) Anti- 

 gens and Organismal Differentials 



Iandsteiner discovered, about forty years ago, that there can be distin- 

 guished in the human blood four groups of red corpuscles, according 

 -i to the type of human serum which agglutinates them. Under normal 

 conditions the serum of a person does not agglutinate the blood corpuscles of 

 another person belonging to the same group, but the serum of individuals 

 belonging to other groups has this power, except the serum of one group, 

 which does not possess such agglutinating substances (agglutinins) for any of 

 the blood groups. The red corpuscles of this latter group, on the other hand, 

 contain both kinds of substances (agglutinogens) which are responsible for 

 the agglutination of corpuscles under the influence of the specific group ag- 

 glutinins in two of the groups. If the serum of this group possessed an active 

 agglutinin, it would agglutinate its own blood corpuscles. There exists another 

 group of individuals whose corpuscles cannot be agglutinated by the serum 

 of any of the other groups, because their corpuscles lack both kinds of ag- 

 glutinable substances (agglutinogens) ; correspondingly, their blood serum 

 has agglutinins for all the other groups. Such agglutinogens, according to the 

 terminology of Ehrlich's sidechain theory, are considered as receptors, which 

 combine with the agglutinin to which they are specifically adapted and such 

 a combination leads to the process of agglutination of the erythrocytes. Inas- 

 much as these agglutinogens, if injected parenterally into animals of a dif- 

 ferent species — e.g., the rabbit — may give rise to the formation of antibodies 

 (immune agglutinins), acting specifically on the type of corpuscles which 

 possess that particular agglutinogen which was injected, they may act also as 

 antigens. In general, they represent the blood-group differentials. 



We can thus distinguish four human blood groups, which differ according 

 to the character of agglutinogens in their erythrocytes as well as according to 

 the character of the agglutinins in their serum. In Group I, the corpuscles do 

 not have any agglutinogens and in the serum there are found agglutinins 

 alpha and beta. Agglutinin alpha has the power to agglutinate the corpuscles 

 of Group II, and agglutinin beta agglutinates the corpuscles of Group III. 

 In Group II, the corpuscles carry agglutinogen A and the serum agglutinin 

 beta. In Group III, the corpuscles have agglutinogen B and the serum pos- 

 sesses agglutinin alpha. In Group IV the corpuscles have both agglutinogens 

 A and B and, correspondingly, their serum lacks agglutinin alpha as well as 

 beta. 



As to the heterogenetic (Forssman) antigens or differentials, these are 

 characterized by their ability to call forth the production of hemolysins for 

 sheep corpuscles if they are injected into the rabbit. As a rule, only the injec- 



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