TABLE 1.

Pathogen recognition receptors expressed by human endothelial cellsa

Pathogen recognition receptorKnown ligand(s)bExpression in human ECcResponse to ligand in human ECcReference
TLR1/2Triacylated lipopeptides++26, 40
TLR2PGN, LTA, lipoarabinomannan++25, 87
TLR2/6Diacylated lipopeptides++16
TLR3Viral dsRNA, poly(I:C)++40, 53, 83
TLR4LPS, LTA++57
TLR5Flagellin++52
TLR7/8Antiviral imidazoquinolines (Imiquimod, R-848), viral ssDNAUnknownUnknown
TLR9Unmethylated bacterial CpG DNA+ (PCR)UnknownUnpublished observation
TLR10UnknownUnknownUnknown
NOD1Intracellular bacteria, gram-negative PGN++60-62
NOD2Intracellular bacteria, muramyl dipeptide++59
  • a Human endothelial cells have been shown to constitutively express an arsenal of pathogen recognition receptors, including Toll-like receptors and NOD proteins 1 and 2. Activation of these receptors by their cognate ligands leads to a ligand-specific innate immune response, characterized by expression of leukocyte adhesion molecules, induction of angiogenesis, and secretion of soluble immune mediators, including cytokines and chemokines.

  • b dsRNA, double-stranded RNA; ssRNA, single-stranded RNA.

  • c +, expression or response.