Schematic representation of the antigen D on the erythrocyte´s surface. The normal RhD protein is shown (left). Every sphere represents an amino acid. Six extracellular loops of amino acids are shown (light yellow and light grey). Transmembranous protein segments are depicted in reddish. The RhD protein differs from the RhCE protein (not shown) be seven extracellular amino acids only (yellow). All other extracellular amino acids (light yellow and light blue) are identical between the RhD- and RhCE-protein. In the DVI-protein (right), two loops carry the RhCE-specific sequence (light blue) rather than the RhD-specific sequence. Thus, the extracellular parts of the DVI-protein differ from the normal RhD-protein by three amino acids only (blue). Other transmembranous and intracellular differences may, however, also effect the protein configuration and are not shown for simplicity.