186 IMMUNOLOGY 



Schiff and Adelsberger (1924) has suggested that the group 

 specific A hapten is a lipoid-carbohydrate complex owing its 

 specific reactions to carbohydrate groups. 



Friedenreich (1939) has demonstrated that group specific 

 substances identical or similar to the group A substance in human 

 red cells are widely distributed in human tissues and secretions. 

 In addition, similar group A substances are found in nature from 

 such diverse sources as horse and bovine saliva and certain pneu- 

 mococci. 



Summary. — It is hoped that the following partial summary of 

 material in this chapter may be of help to the student. 



In 1901, Landsteiner discovered three of the four recognized 

 blood groups within the human species and postulated two ag- 

 glutinogens A and B and two agglutinins a and ^. He also sug- 

 gested the law of reciprocal relationships according to which, 

 when an agglutinogen is present in the red cells the correspond- 

 ing agglutinin is absent from the serum, and conversely, when 

 the agglutinin is present in the serum, the corresponding ag- 

 glutinogen is absent from the red cells of that particular blood. 



The following year DeCastello and Sturli described four ex- 

 amples of the fourth group. They considered a classification 

 identical with that of Moss (1909-10), but did not feel warranted 

 in recommending its adoption. Since the four examples of what 

 they termed group 1 (AB) were all infants, they thought perhaps 

 the latter had not developed a stable group. It is interesting to 

 note that DeCastello and Sturli conceived that some type of what 

 has been more recently called reciprocal binding may exist be- 

 tween an agglutinogen and agglutinin which would prevent auto- 

 agglutination. The classifications suggested by Jansky (1907) and 

 Moss are given and compared with a new classification being 

 used quite generally in the literature and based upon the ag- 

 glutinogen content of the cells. The agglutinogens are present 

 in the red cells at birth. The agglutinins may be present then, 

 or make their appearance at some time during the first four years 

 of life. When once established, the group remains stable except, 

 perhaps, for quantitative variations in titer of agglutinins. 



The racial distribution of the blood groups is discussed briefly 

 in connection with the two-factor and the triple allelomorph theory. 



