Antimicrobial and Immunomodulatory Role of Fish Lectins

Abstract

Lectins are proteins that can bind to carbohydrates selectively and reversibly without changing the ligand’s covalent structure. Lectins are divided into several families based on their structure, binding specificities, and calcium dependence, such as C-type lectins, I-type lectins, F-type lectins, intelectins, rhamnose binding lectins, galectins, Lily-type lectins, and so on. Innate immunity and disease resistance are known to be aided by lectins such as ficolins, calnexin, galectins, F-type lectins, intelectins, and mannose-binding proteins (MBPs). In fish, skin serves as an essential immunological structure, and lectins have been found in the stomach, eggs, gut, liver, gills, serum, skin, and plasma of several fish species. The capacity of lectins to promote agglutination, suppression of planktonic development, biofilm inhibition or eradication, and/or death of bacteria has been shown to have direct antibacterial action. The interaction of lectins with bacterial cell wall components [such as N-acetylglucosamine (NAG), N-acetylmuramic acid (NAM), tetrapeptides related to NAM, and lipopolysaccharides] as well as membrane receptors has been credited with growth suppression and death induction. This might cause permeabilisation and the development of holes in the bacterial cell wall and membrane, allowing intracellular material to seep out. Lectins are part of the innate immune system’s humoral component and are engaged in the detection of PAMPs that cause agglutination and neutralisation of potentially microbial pathogens or the activation of complement components. Various research findings show that fish lectins play an important role in immunological identification of microbial infections and phagocytosis clearance. The significance of lectins in antimicrobial and immunomodulatory activity in fish is discussed in this review.KeywordsFish lectinsAntimicrobial activityImmunomodulatory activityGalectinsCTLFTL