Human blood group antigens on red cells can be broadly classified into carbohydrates and proteins. The former category includes ABH, Lewis (Le), Ii, and P-related antigens, and the latter category is represented in this minireview by the Duffy antigens (Fy
a and Fy
b), and the M and N antigens carried on glycophorin A. The ABH and Ii antigens are located on the polylactosaminoglycans of glycoproteins Band 3 and Band 4.5, and on polyglycosylceramides. The Le
a, Le
b and the P-related antigens are associated only with glycosphingolipids. These carbohydrate-dependent antigens are expressed not only on red cells, but they are also detected on various epithelial tissues, organs, and secretions. Some of them are tumor-associated as their expressions on certain malignant tissues are incompatible with the blood groups of the cancer patients. The Duffy antigens and glycophorin A are erythroid specific. They have been identified as separate ligands to which the merozoites of
Plasmodium knowlesi (or
P. vivax) and
Plasmodium falciparum attach respectively at the asexual stage of the life cycle of these malarial parasites.
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