Lectins from tunicates: structure-function relationships in innate immunity.

Abstract

Since the discovery of lectins in the 1890s, it has remained a challenge to define the biological function(s). A basic premise of lectin study is that their physiological function(s) relate to their carbohydrate-binding properties. Thus, detailed and useful descriptions of tissue distribution, sugar specificity, and molecular structures are available for many lectins. From the earliest reports, possible roles in fertilization and immune responses have been investigated. Lectins secreted from the albumin gland of the snail Helix pomatia able to agglutinate erythrocytes (Camus, 1899) were later named “protectins” to suggest that these protect against microbial or fungal infection (Prokop, 1965). Studies on arthropod species, such as the horseshoe crab Limulus polyphemus, the lobster Homarus americanus,the crab Eupagurus prideauxii, and the spider crab Maia squinado, extended the hemagglutination properties to hemolymph lectins, providing evidence that expression of these proteins is inducible by challenge with agglutinated bacteria, and furthermore that the induced lectins have opsonic properties (Cantacuzene, 1919).