54 INTRODUCTION TO IMAIUNOCHEMICAL SPECIFICITY 



was therefore a considerable advance in blood grouping technique 

 when it was discovered that saline extracts of the seeds of certain 

 plants, such as Ulex europeus, which grows wild in Western and 

 Southern Europe and in North Africa, contain an agglutinin specific 

 for this antigen of the group O erythrocytes (Cazal and Lalaurie, 

 1952; Boyd and Shapleigh, 1954a). This plant agglutinin has ap- 

 parently replaced all other reagents in this application. 



At first it was believed that the agglutinogen detected by this 

 agglutinin, whatever the source of the agglutinin, was an O antigen 

 which had the same relation to the O gene as the B antigen has to 

 the B gene. The agglutinin was therefore called anti-O. It was soon 

 found, however, that erythrocytes of the subgroups A2 and A2B are 

 also agglutinated by the agglutinin, A2 cells being affected about as 

 strongly as O cells. This is apparently true even when the genotype of 

 the Ao individual is A2A2, so that no O gene is present. It seemed im- 

 proper to retain the name anti-O for a reagent that detects an anti- 

 gen produced by both the O and Ao genes. Following the practice 

 of Morgan (Morgan and Watkins, 1948), the term anti-H is now 

 generally used for the agglutinin and the term H for the antigen it 

 detects. 



Taking account of this and other discoveries about the blood 

 groups, we may revise Table 4-1 (see Table 4-3). 



TABLE 4-3 

 Subgroups of Landsteiner Blood Groups 



Secretors and Nonsecretors 



The antigens of the ABO blood group system are not confined to 

 the erythrocytes. They may occur in practically all tissues and fluids 

 of the body, with the probable exception of the central nervous sys- 



