Pattern recognition receptors in annelids

Dev Comp Immunol. 2020 Jan;102:103493. doi: 10.1016/j.dci.2019.103493. Epub 2019 Sep 6.


The existence of pattern recognition receptors (PRRs) on immune cells was discussed in 1989 by Charles Janeway, Jr., who proposed a general concept of the ability of PRRs to recognize and bind conserved molecular structures of microorganisms known as pathogen-associated molecular patterns (PAMPs). Upon PAMP engagement, PRRs trigger intracellular signaling cascades resulting in the expression of various proinflammatory molecules. These recognition molecules represent an important and efficient innate immunity tool of all organisms. As invertebrates lack the instruments of the adaptive immune system, based on "true" lymphocytes and functional antibodies, the importance of PRRs are even more fundamental. In the present review, the structure, specificity, and expression profiles of PRRs characterized in annelids are discussed, and their role in innate defense is suggested.

Keywords: Annelida; CCF; Discrimination; Earthworm; Immunity; LBP; PAMP; PRR; Phenoloxidase cascade; TLR.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Acute-Phase Proteins / chemistry
  • Acute-Phase Proteins / genetics
  • Acute-Phase Proteins / metabolism
  • Animals
  • Annelida / immunology*
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Gene Expression Regulation
  • Immunity, Innate*
  • Membrane Glycoproteins / chemistry
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism
  • Pathogen-Associated Molecular Pattern Molecules / immunology
  • Pathogen-Associated Molecular Pattern Molecules / metabolism
  • Receptors, Pattern Recognition / chemistry
  • Receptors, Pattern Recognition / genetics
  • Receptors, Pattern Recognition / metabolism*
  • Signal Transduction / immunology
  • Tissue Distribution
  • Toll-Like Receptors / chemistry
  • Toll-Like Receptors / genetics
  • Toll-Like Receptors / metabolism


  • Acute-Phase Proteins
  • Carrier Proteins
  • Membrane Glycoproteins
  • Pathogen-Associated Molecular Pattern Molecules
  • Receptors, Pattern Recognition
  • Toll-Like Receptors
  • lipopolysaccharide-binding protein