SEROLOGY AND SYSTEMATICS 



85 



One point raised previously is of particular interest. It was 

 stated that simple sugars may sometimes inhibit specific plant 

 agglutinins. The first report of inhibition of this type was that of 

 Watkins and Morgan (1952) who, in this case using anti-H agglutinin 

 of eel serum, discovered that agglutination was inhibited by L-fucose. 

 In addition to certain simple sugars, the sugar derivation N-acetyl- 

 galactosamme inhibits anti-A, and anti-B agglutinins from a number 

 of sources (Makela, 1957). This observation acquires added signif- 

 icance following the disclosure that X-acetyl-galactosamine is present 

 in hydroly sates of blood (particularly high \-ields are derived from 

 blood gi-oup A, lower fields in 0, and practically none in B). It is 

 suggestive of the presence of a carbohydrate-like terminal group on 

 the antigen. A general theory to account for the inhibition of agglu- 

 tinins by simple sugars is that the sugars resemble the reactive end 

 group of a red blood ceU receptor. The sugars then attach to the 

 agglutinin complementary site blocking it and thereby preventing 

 agglutinin-receptor contact. On the basis of the structural relation- 

 ships of groups of sugars which are effective inhibitors as opposed to 

 the ineffective sugars it has been suggested by Krupe (1956) that the 

 configuration of carbon 3 and 4 is important in determining the 

 abihty of the sugar to inhibit agglutinins. 



Four patterns available in placement of hydroxyl 

 groups in carbons 3 and 4 of aldopyranoses. 



4 



O 



HO 



h6\oh 



HO 



The more strongly inhibiting sugars fall into groups 1 and 2 

 above. For example inhibitors of anti-B extracts, such as L-arabinose 

 and D-galactose, represent group 2. Inhibitors of anti-H extracts, such 

 as D-ai'abinose, D-digitoxose. L-fucose, and L-galactose ai'e of group 



