Galectin-9 (LGALS9) is also known as tumor antigen HOM-HD-21 and ecalectin. Galectins are a family of proteins defined by their binding specificity for β-galactoside sugars, such as N-acetyllactosamine (Galβ1-3GlcNAc or Galβ1-4GlcNAc), which can be bound to proteins by either N-linked or O-linked glycosylation. As for Galectin-9, it has high affinity for the Forssman pentasaccharide, and it is also the ligand for HAVCR2/TIM3. Forthermore, Galectin-9 stimulates bactericidal activity in infected macrophages by causing macrophage activation and IL1B secretion which restricts intracellular bacterial growth.