96 



INTRODUCTION TO IMMUNOCHEMICAL SPECIFICITY 



TABLE 7-5 

 Inhibition of Peanut Lectin (Anti-Gy) by Sugars^ 

 Sugar, diluted 



that the peanut receptor contains glucose as the next-to-terminal 

 unit, possibly linked to the terminal galactose by a l^-l link (the 

 linkage in trehalose). The peanut agglutinin, in spite of a presumed 

 galactose terminal unit, is not inhibited by B substance and in that 

 respect resembles the Bauhinia agglutinin. The two receptors are 

 different, however, since the peanut receptor, unlike the Bauhinia re- 

 ceptor, is not found on all human erythrocytes. Another sign of 

 difference is that the peanut agglutinin is inhibited by sugars (cello- 

 biose, trehalose, melezitose, and maltose) which do not inhibit the 

 Bauhinia agglutinin. 



There thus seem to be at least three receptors containing galactose 

 as a terminal unit, one of them present on all human red cells, the 

 others only on those of certain individuals. Their structure in the 

 light of our present scanty information is shown in Fig. 7-9. 



It has already been mentioned that plant agglutinins inhibited by 

 sugars of Maleka's group 3 react with a red cell receptor present 

 on all human red cells. It would seem likely that the terminal unit 

 in this receptor is a sugar of group 3. Since Makela found mannose 

 the best inhibitor for such agglutinins, one could hazard the guess that 



