Linear poly-N-acetyllactosamine (i-antigen)

Linear poly-N-acetyllactosamines, also known as the i-antigen, are carbohydrate structures consisting of repeating units of N-acetyllactosamine (Galβ1-4GlcNAcβ1-3) found on N-glycans, O-glycans, and glycolipids (Essentials of Glycobiology, 2022). These glycans are primarily expressed on the surface of fetal erythrocytes and are typically converted to branched I-antigens by the enzyme GCNT2 during neonatal development (Blood, 2003). Biologically, they function as high-affinity ligands for galectins, a family of lectins that regulate critical processes such as cell-cell adhesion, immune cell trafficking, and apoptosis (Journal of Biological Chemistry, 2014). In clinical medicine, the i-antigen is the primary target for cold-reacting autoantibodies in cold agglutinin disease, which can lead to complement-mediated hemolysis and chronic anemia (StatPearls, 2023). Furthermore, increased expression of these linear glycans is frequently observed in malignant cells, where they facilitate tumor progression and immune evasion by interacting with galectins in the tumor microenvironment (Glycobiology, 2018). Therapeutic strategies targeting this pathway include the development of galectin inhibitors, such as GB1211 and TD139, which aim to disrupt the pathological interactions between these glycans and their receptors in fibrosis and cancer (Galecto Biotech, 2023).

Other names

i-antigenLinear poly-LacNAcPoly-N-acetyllactosaminei-linear glycanType 2 lactosamine repeats

Competitive inhibition of galectin binding to poly-N-acetyllactosamine motifs or antibody-mediated neutralization and clearance