2018 Volume 30 Issue 172 Pages SE199-SE209
The glycocalyx is a layer of glycoconjugates found on the surface of both host cells and microorganisms. Information presented on some of the glycans on glycoconjugates is recognized by mammalian glycan-binding proteins, lectins, and these interactions modulate various physiological processes, including host innate immune responses. Lectins and host glycoconjugates are synthesized in the same secretory pathway. One notable exception is a family of soluble β-galactoside-binding lectins, galectins, which are synthesized and accumulated in the cytosol and thereby segregated from their glycan ligands. In cases where pathogenic infection persists and tissue injury occurs, galectins are passively released from injured cells. In addition, galectins are actively secreted through unconventional secretory pathways by inflammation-activated or differentiating cells. Thus, extracellular emergence of galectins is associated with the presence of pathogenic hazards. Evidence from a series of studies suggests that galectins exert multiple immunological effects. Extracellular galectin-3 acts as a damage-associated molecular pattern (DAMP) and adhesion molecule for neutrophils in lungs to initiate a proinflammatory response and to mediate rapid neutrophil migration in lungs infected with pathogenic microorganisms. In this review, the roles of galectin-3 in initial innate immune responses and resolution are discussed together with a historical overview of research on galectins in the secretory pathway and innate immunology.
