Lectins have these functions in animals:
* The regulation of cell adhesion
* The regulation of glycoprotein synthesis
* The regulation of blood protein levels
* The binding of soluble extracellular and intercellular glycoproteins
* As a receptor on the surface of mammalian liver cells for the recognition of galactose residues, which results in removal of certain glycoproteins from the circulatory system
* As a receptor that recognizes hydrolytic enzymes containing mannose-6-phosphate, and targets these proteins for delivery to the lysosomes; I-cell disease is one type of defect in this particular system.
* Lectins are known to play important roles in the innate immune system. Lectins such as the mannose-binding lectin, help mediate the first-line defense against invading microorganisms. Other immune lectins play a role in self-nonself discrimination and they likely modulate inflammatory and autoreactive processes. Intelectins (X-type lectins) bind microbial glycans and may function in the innate immune system as well. Lectins may be involved in pattern recognition and pathogen elimination in the innate immunity of vertebrates including fishes.