Mannose-rich glycans are short carbohydrate chains
with the sugar mannose or fructose as the terminal sugar. They are commonly
found in microbial glycoproteins and glycolipids but are rare in those
of humans. (Human glycoproteins and glycolipids typically have terminal
N-acetylglucosamine and sialic acid groups.) C-type lectins, found on the
surface of phagocytes, are endocytic pattern recognition receptors that bind to mannose-rich glycans in order to attach microbes to phagocytes. Mannose-binding lectin (MBL), also
known as mannan-binding protein, is a soluble pattern recognition receptor in plasma and tissue fluid that binds to mannose-rich glycans on microbes in oder to activate the lectin complement pathway.