Tn antigen
Tn antigen refers to the monosaccharide structure N-acetylgalactosamine linked to serine or threonine by a glycosidic bond, considered as an antigen. The initials stand for Thomsen-nouveau. Tn antigen is expressed in most carcinomas.
Addition of an additional galactose monosaccharide creates a disaccharide antigen: the Thomsen-Friedenreich antigen. The sialyl Tn antigen is formed by elongation with sialic acid rather than galactose.