CD238

CD238 is the Kell blood group glycoprotein, a type II transmembrane zinc endopeptidase of the neprilysin (M13) metalloprotease family. It is highly expressed on erythroid precursors and erythrocytes and is also present on endothelial cells and testis. Amino acid substitutions within its large extracellular region define the K and k antigens and more than 30 additional Kell system specificities. Physiologically, Kell protein cleaves big endothelin-3 to release the vasoactive peptide endothelin-3, the best-characterized substrate of the enzyme. Clinically, anti-K antibodies are a frequent cause of hemolytic transfusion reactions and of hemolytic disease of the fetus and newborn, so Kell typing is routine in transfusion medicine.