"Dirty Little Secrets"--Endotoxin Contamination of Recombinant Proteins

Immunol Lett. 2006 Jul 15;106(1):1-7. doi: 10.1016/j.imlet.2006.04.007. Epub 2006 May 11.


The identification of Toll-like receptors has revolutionised our understanding of innate immunity. TLR4 transduces the LPS signal and that of a number of structurally and functionally unrelated agonists. However, recent evidence adds to longstanding concerns that endotoxin contamination of bacterially derived recombinant TLR4 agonists is responsible for effects attributed to these molecules. We highlight key factors in differentiating specific agonist effects from those of endotoxin and emphasize why conventional methods of detecting and eliminating LPS may lead to erroneous results. We propose that considerable caution is needed in the investigation of TLR4 agonists, particularly when using proteins produced in a bacterium that also houses the most ideal TLR4 agonist, LPS.

MeSH terms

  • Animals
  • Drug Contamination*
  • Endotoxins / analysis*
  • Endotoxins / immunology*
  • Endotoxins / pharmacology
  • Humans
  • Lipopolysaccharides / analysis
  • Lipopolysaccharides / immunology
  • Lipopolysaccharides / pharmacology
  • Recombinant Proteins / chemistry*
  • Toll-Like Receptor 4 / agonists
  • Toll-Like Receptor 4 / immunology


  • Endotoxins
  • Lipopolysaccharides
  • Recombinant Proteins
  • Toll-Like Receptor 4