Susceptibility to invasion by Plasmodium falciparum of some human erythrocytes carrying rare blood group antigens.

Tn and Cad erythrocytes which carry unusual carbohydrate moieties attached to glycophorin A and B, the main red cell membrane sialoglycoproteins, resist invasion by the malarial parasite Plasmodium falciparum. Tn red cells are defective in sialic acid and galactose whereas Cad erythrocytes are characterized by a normal sialic acid content but the presence of an additional N-acetylgalactosamine residue attached to each sialotetrasaccharide chain O-glycosidically linked to glycophorin A and B. Homozygous MgMg red cells, which are defective in the cluster of three sialotetrasaccharide chains located at positions 2, 3 and 4 of glycophorin A, are normally invaded. Erythrocytes typed McM carry a glycophorin A molecule intermediate between those from M and N (amino acid substitution at position 1 or 5) but are, like control MN red cells, susceptible to invasion. These results suggest that the primary requirement for entry of P. falciparum merozoites into human red cells is the recognition of a carbohydrate structure present on glycophorin A or B which includes sialic acid and galactose, but is not necessarily clustered at the N-terminal end of the molecule.