GalNAc-a-1,3-GalNAc; Forssman Disaccharide 

2-Acetamido-3-O-(2-acetamido-2-deoxy-a-D-galactopyranosyl)-2-deoxy-D-galactopyranose

2-Acetamido-3-O-(2-acetamido-2-deoxy-a-D-galactopyranosyl)-2-deoxy-D-galactopyranose is a glycan that is found in human serum and maternal blood. The wild type strain of 2,3,4,6,7,8 diacetylgalactosaminyltransferase (GnTIII) gene has been shown to be essential for the synthesis of this glycan. This glycan is also found in the carcinoma cell lines HT1080 and SW480. Structural analysis of the glycan has revealed that it contains a hydroxyl group on the C1 position and an acetamido group on the C2 position. Glycans are polymers that play roles in many biological functions such as cell recognition, immune responses, and carbohydrate metabolism.