Galectins are a family of ?-galactose binding proteins that are characterized by an affinity for poly-N-acetyllactosamine-enriched glycoconjugates and a carbohydrate-binding site. Members of the galectin family have been implicated in a variety of biological functions, including cell adhesion, growth regulation, cytokine production, T cell apoptosis, and immune responses. Galectin-3/LGALS3 is involved in several diverse biological functions. Galectin-3/LGALS3 binds IgE. Galectin-3/LGALS3 is an unusual protein in that it can be found both extracellularly and intracellularly. Intracellularly, Galectin-3/LGALS3 can localize to the cytoplasm, nucleus, or both, depending on cell type and experimental conditions. Nuclear Galectin-3/LGALS3 has been identified as a pre-mRNA splicing factor. Galectin-3/LGALS3 production has been shown to increase during inflammation and in obesity, and the protein itself can have an inflammatory effect under certain conditions. Galectin-3/LGALS3 forms a complex with ?3, ?1 integrin to act as a surface receptor on endothelial cells for the NG2 proteoglycan, which triggers cell motility and angiogenesis. In addition to these functions, Galectin-3/LGALS3 is also a required factor for the terminal differentiation of epithelial cells.