CHAPTER 7 

 Blood Group Antigens 



Sources of Antigens for Study 



The human erythrocyte is a compHcated structure, the blood group 

 antigens apparently making up only a small part of its mass. It is 

 not surprising, therefore, that attempts to determine the structure of 

 the blood group antigens by analyzing material isolated from erythro- 

 cytes have never given information of much value. Not only is the 

 starting material complex and the desired antigens only a small por- 

 tion of it, but the antigens seem to be bound in some way to the 

 lipids, and possibly to the proteins, which are present on the surface 

 of the red cell, making purification extremely difficult (Morgan and 

 Watkins, 1959) . If it were not for the much more abundant occurrence 

 of the blood group substances, in water-soluble form, in the saliva, 

 gastric juice, ovarian cyst fluid, and meconium of secretors, and the 

 occurrence of closely related antigens in hog and horse stomach, little 

 would be known today of the chemistry of blood group substances. 



A number of methods of isolating and purifying blood group sub- 

 stances from the sources just mentioned have been described. The 

 extraction with cold 90 per cent phenol, employed by Morgan and 

 King (1943), used more than any other method, eliminates most of 

 the accompanying nonspecific protein and other impurities. High- 

 speed centrifugation and further fractionation from water and other 

 solvents results in further purification. 



Blood Group Substances A, B, H, and Le"*. 



As a result of such methods, four blood group substances have been 

 obtained in amounts sufficient for chemical study : A, B, H, and Le*. 



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