Ligand specificities of Toll-like receptors in fish: indicatiaons from infection studies

D. Pietretti, G. Wiegertjes

Research output: Contribution to journalArticleAcademicpeer-review

166 Citations (Scopus)


Toll like receptors (TLRs) are present in many different fish families from several different orders, including cyprinid, salmonid, perciform, pleuronectiform and gadiform representatives, with at least some conserved properties among these species. However, low conservation of the leucine-rich repeat ectodomain hinders predictions of ligand specificities of fish TLRs based on sequence information only. We review the presence of a TLR genes, and changes in their gene expression profiles as result of infection, in the context of different fish orders and fish families. The application of RT-qPCR and availability of increasing numbers of fish genomes has led to numerous gene expression studies, including studies on TLR gene expression, providing the most complete dataset to date. Induced changes of gene expression may provide (in)direct evidence for the involvement of a particular TLR in the reaction to a pathogen. Especially when findings are consistent across different studies on the same fish species or consistent across different fish species, up-regulation of TLR gene expression could be a first indication of functional relevance. We discuss TLR1, TLR2, TLR4, TLR5 and TLR9 as presumed sensors of bacterial ligands and discuss as presumed sensors of viral ligands TLR3 and TLR22, TLR7 and TLR8. More functional studies are needed before conclusions on ligands specific to (groups of) fish TLRs can be drawn, certainly true for studies on non-mammalian TLRs. Future studies on the conservation of function of accessory molecules, in conjunction with TLR molecules, may bring new insight into the function of fish TLRs.
Original languageEnglish
Pages (from-to)205-222
Number of pages17
JournalDevelopmental and Comparative Immunology
Issue number2
Publication statusPublished - 2014


  • carp cyprinus-carpio
  • salmon salmo-salar
  • indian major carp
  • flounder paralichthys-olivaceus
  • aeromonas-hydrophila infection
  • pattern-recognition receptors
  • hemorrhagic septicemia virus
  • respiratory syncytial virus
  • sole cynoglossus-semilaevis
  • mrigal cir


Dive into the research topics of 'Ligand specificities of Toll-like receptors in fish: indicatiaons from infection studies'. Together they form a unique fingerprint.

Cite this