The Diego blood group system consists of 23 antigens carried on a multipass membrane glycoprotein called band 3 (aka AE1; SLC4A1; CD233). It consists of 911 amino acids and both amino and carboxyl termini are predicted to be intracellular. The transmembrane domains of band 3 function as the RBC anion transporter while the long amino terminal region of the protein is critical to maintaining RBC shape integrity through its interaction with the cytoskeleton. With the introduction of the DIST antigen there are 23 antigens.