Lectins, of either plant or animal origin, are carbohydrate binding proteins that interact with glycoprotein and glycolipids on the surface of animal cells. The Galectins are lectins that recognize and interact with β-galactoside moieties. Galectin-3 regulates a number of biological processes, including embryogenesis, inflammatory responses, cell progression and metastasis. Galectin-3 is normally expressed in epithelia of a variety of tissues, including colon and endometrium, and in various inflammatory cells, including macrophages. Galectin-3 can function intracellularly, in controlling cell cycle and preventing T-cell apoptosis, and also extracellularly, in activating various cells, including monocytes/macrophages, mast cells, neutrophils, and lymphocytes. Expression of Galectin-3 is affected by neoplastic transformation, being up-regulated in certain types of lymphomas, and in thyroid and hepatic carcinomas. Conversely, it is down-regulated in other cancers, such as colon, breast, ovarian, and uterine. Recombinant human Galectin-3 is a globular 26.0kDa protein containing 250 amino acid residues, but no disulfide bonds.