The immune response is intimately associated with glycan recognition. Protein glycosylation is critical for the differentiation and maturation of immune cells. Glycan-binding proteins (lectins), on the other hand, are critical for activation and function.
Examples of the roles of glycans in the immune system include:
- Many CDs (clusters of differentiation) are glycoproteins or lectins (glycan-binding proteins).
- The cell surface of mammalian cells is rich in glycoconjugates (glycocalyx) displaying self-identity determinants and other antigens, such as the A-B-O blood groups.
- Many pathogen-associated molecular patterns (PAMPs) are glycans, and their immune receptors are carbohydrate-binding proteins (lectins).
- Cell-surface glycans determine lymphocyte migration to injury sites.
- While the Fab (variable) region of antibodies determines their specificity, the glycosylation at the Fc (constant) region modulates their effector functions.
- Galectins (galactose-binding lectins) are intimately associated with pathogen recognition, inflammation, effector functions and cancer progression.
- The mannose receptor binds terminal sugars found on some microorganisms. It has an important role in the innate and adaptive immune responses, as well in glycoprotein clearance from the bloodstream.