Beta-1,3-glucuronyltransferase 1,CD57, also known as HNK1 or Leu7, is a sulphated trisaccharide (3-O-sulfoglucuronic acid beta1-3 Gal beta1-4 GlcNAc) attached to several glycoproteins, including CD56, myelin glycoprotein PO, and neural cell adhesion molecule L1, as well as on glycolipids and chondroitin sulphate proteoglycans in the nervous system. It serves as a NK cell marker and it is expressed on well differentiated prostate cancers and uveal and cutaneous melanoma. CD57+ T cells are implicated as suppressors of T-cell responses.,HNK1, LEU7, 3-O-sulfoglucuronic acid beta1-3 Gal beta1-4 GlcNAc