GA130000: H-Thr(α-D-GalNAc)-OHTumor Associated Carbohydrate Antigen (TACA). Tn is a truncated O glycosylated core determinant with structure: GalNAc O Ser Thr. In normal Mamalian cells, the Tn determinant is masked by larger glycan residues. Once unmasked, Tn serves as an important recognition element, mediating several cell cell interactions. As such, Tn is implicated in tumour cell organotropic metastasis. Targeting immune responses to truncated variants of O glycan chains