66 INTRODUCTION TO IMMUNOCHEMICAL SPECIFICITY 



TABLE 5-2 

 Titers of Different Plant Agglutinins for the Red Cells of Different Species* 



■^ After Landsteiner, 1945. 



will be seen that some of the seed extracts show specificity, since 

 they agglutinate the erythrocytes of one species more strongly than 

 those of another and in one case do not agglutinate blood of a 

 certain species at all. 



Blood Group-Specific Plant Agglutinins 

 One day toward the end of 1945, looking at this table (Table 5-2) 

 in the new edition of Landsteiner's book, I was seized with the 

 idea that if such seed extracts could show species specificity, they 

 might even show individual specificity ; that is, they might possibly 

 affect the red cells of some individuals of a species and not affect 

 those of others of the same species. I asked one of my assistants to 

 go out and buy dried lima beans. Why I said lima beans instead of 

 pea beans or kidney beans I shall never know. But if we had bought 

 practically any other kind of bean we should not have discovered any- 

 thing new. 



The lima beans were ground and extracted with salt solution. 

 The extract agglutinated erythrocytes of some human individuals 

 very strongly, btit those of others only weakly if at all. It was im- 

 mediately evident that the differences were correlated with blood 

 groups (Table 5-3). The agglutinin from lima beans is almost com- 

 pletely specific for the blood group A antigen. 



This discovery was made so easily that I was disarmed. The whole 

 process of thinking of the experiment, obtaining the materials, and 

 testing the idea were the events of perhaps two hours. So it is not 

 surprising, perhaps, that I failed to realize the importance of the 

 observation and did not immediately follow it up. I was also then in 



