Wolfgang Dahr

Serological and Biochemical Investigations on the N.E. Variety of the Dantu Red Cell Phenotype

Studies during the last decade have established that the MNSs blood group locus corresponds to two, presumably adjacent, genes whiff encode the amino-acid sequences of two (MN and Ss) sialoglycoproteins (SGPs) or glycophorins (A and B) in human red cell (RBC) membranes (reviews: 1–4). The structural difference between the M and N antigens is determined by amino-acid polymorphisms at the 1st (Ser/Leu) and 5th (Gly/Glu) positions of the MN SGP, the complete sequence of which was elucidated (5–8). The sequence of the N-terminal 26 residues (res.) of the Ss SGP is identical with that of the N-specific MN SGP (8,9). This explains the occurrence of an additional N antigen, denoted as ‘N’, on the Ss SGP. A Met/Thr polymorphism at the 29th position of the Ss SGP represents the structural difference between the S and s antigens (8). Recently (10), the sequence of the intramembraneous domain (res. 36–72) of the Ss SGP was determined and found to be rather similar to the corresponding region (res. 65–101) of the MN SGP (Fig. 1).

Biochemical Characterization of Class VII and VIII Cells within the Miltenberger System

The various antigens of the MNSs blood group system are located on two homologous, sialic acid-rich glycoproteins (SGPs) in human red blood cell (RBC) membranes: glycophorin A (GP A; MN SGP; α) and GP B (Ss SGP or δ) (for reviews see Dahr 1986; Lisowska 1987; Moulds & Dahr 1987). The ‘MNSs locus’, located on chromosome 4, appears to comprise two adjacent genes that encode the amino-acid sequences of these two molecules.