Galectins in innate immunity: dual functions of host soluble beta-galactoside-binding lectins as damage-associated molecular patterns (DAMPs) and as receptors for pathogen-associated molecular patterns (PAMPs)

Immunol Rev. 2009 Jul;230(1):172-87. doi: 10.1111/j.1600-065X.2009.00790.x.

Abstract

The glycocalyx is a glycan layer found on the surfaces of host cells as well as microorganisms and enveloped virus. Its thickness may easily exceed 50 nm. The glycocalyx does not only serve as a physical protective barrier but also contains various structurally different glycans, which provide cell- or microorganism-specific 'glycoinformation'. This information is decoded by host glycan-binding proteins, lectins. The roles of lectins in innate immunity are well established, as exemplified by collectins, dectin-1, and dendritic cell (DC)-specific intracellular adhesion molecule-3-grabbing non-integrin (DC-SIGN). These mammalian lectins are synthesized in the secretory pathway and presented on the cell surface to bind to specific glycan 'epitopes'. As they recognize non-self glycans presented by microorganisms, they can be considered as receptors for pathogen-associated molecular patterns (PAMPs), i.e. pattern recognition receptors (PRRs). One notable exception is the galectin family. Galectins are synthesized and stored in the cytoplasm, but upon infection-initiated tissue damage and/or following prolonged infection, cytosolic galectins are either passively released by dying cells or actively secreted by inflammatory activated cells through a non-classical pathway, the 'leaderless' secretory pathway. Once exported, galectins act as PRR, as well as immunomodulators (or cytokine-like modulators) in the innate response to some infectious diseases. As galectins are dominantly found in the lesions where pathogen-initiated tissue damage signals appear, this lectin family is also considered as potential damage-associated molecular pattern (DAMP) candidates that orchestrate innate immune responses alongside the PAMP system.

Publication types

  • Review

MeSH terms

  • Animals
  • Dendritic Cells / immunology
  • Dendritic Cells / metabolism
  • Eosinophils / immunology
  • Eosinophils / metabolism
  • Galectins / immunology*
  • Galectins / metabolism
  • Glycocalyx / immunology
  • Glycocalyx / metabolism
  • Humans
  • Immunity, Innate*
  • Macrophages / immunology
  • Macrophages / metabolism
  • Neutrophils / immunology
  • Neutrophils / metabolism
  • Polysaccharides / immunology*
  • Polysaccharides / metabolism
  • Receptors, Pattern Recognition / immunology*
  • Receptors, Pattern Recognition / metabolism

Substances

  • Galectins
  • Polysaccharides
  • Receptors, Pattern Recognition