Glycans: Molecules at the Interface of Immunity and Disease

Book excerpt: Glycans are complex, multi-unit carbohydrate structures that cover the surfaces of cells and guide cellular interactions. Glycobiology studies the synthesis, structure, function, regulation, and evolution of glycans and glycan-binding molecules. Glycans are synthesized and added as modifications to proteins, lipids, and RNA. Though they are often associated with functions outside of cells (glycoproteins and glycolipids are most often extracellular or secreted), glycans are also active within cells. Glycans are known to have diverse physiological roles ranging from cell adhesion (maintaining tissue structure and integrity) to molecular recognition (marking position during development, or self-identity in immunity and reproduction). Glycans also regulate cellular activity and physiological state. The families of proteins that bind glycans are called lectins. Glycans and lectins are vital in many diseases such as cancer, neurodegeneration, inflammation, allergies, asthma, and autoimmune disorders.