Evolution and Immune Function of Fish Lectins

Lectins are sugar-binding proteins widely distributed among animals, plants, and microbial taxon, involved in diverse biological processes. In both invertebrates and vertebrates, they play key roles in nonself recognition and immune responses, such as nonself recognition, inflammatory processes, and immunomodulation. In fish, many lectin families have been identified, and their tissue-specific expression and localization of the various lectin repertoires and their ligands are consistent with their distinct biological roles in innate and adaptive immunity. Here, we discuss the involvement of F-type lectins, rhamnose-binding lectins, galectins, and C-type lectins in pathogen recognition and opsonization through the binding of endogenous and exogenous ligands and their additional effector roles, such as complement activation and regulation of immune functions. These lectin families, identified and characterized in fish, appear to be involved in nonself recognition, inflammatory reaction, and immunomodulation processes. Function and phylogenetic history of these lectin families are also described.