86 INTRODUCTION TO IMMUNOCHEMICAL SPECIFICITY 



The Le^ antigen (one of the antigens of the Lewis blood group sys- 

 tem) has been studied nearly as thoroughly as the ABH antigens be- 

 cause it also occurs in water-soluble form in body fluids. 



Analytical Results 



The results of chemical analyses of the ABH and Le^ blood group 

 antigens have been disappointing : they have not revealed any chemi- 

 cal differences that can be correlated with dififerences in blood group 

 activity. At a glance, the four antigens seem very much alike. They 

 each contain the same two sugar components, L-fucose and D-galactose, 

 and the same amino sugar components, D-glucosamine and D-galac- 

 tosamine. They also contain the same eleven amino acids (Kabat, 

 1956; Morgan and Watkins, 1959). The role of the amino acids is 

 not clear, for the specificity of the antigens seems to be determined 

 mainly by the carbohydrate portions. Morgan believes, however, that 

 the blood group antigens are not merely a loose combination of a 

 macromolecular polysaccharide with protein but consist of carbo- 

 hydrate chains and peptide units bound together by primary chemical 

 bonds. 



Typical analytical values for preparations of the specific substances 

 are shown in Table 7-1. The observed dififerences are within the 

 range of variation found with different preparations of the same anti- 

 gen (Morgan and Watkins, 1959). 



From such data we are forced to conclude that the specific serologi- 

 cal dififerences between the A, B, and H antigens are due not to 

 dififerences in over-all composition but to variations in the arrange- 



TABLE 7-1 



Typical Analytic Values for Preparations of Human Blood Group 

 Antigenic Substances" 



Substance N, % Fucose, % Acetyl, % Hexosaniine, % Reduction, % 



Morgan and Watkins, 1959. 



