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Table 1 Exogenous and endogenous TLR ligands.

From: Toll-like receptors in cerebral ischemic inflammatory injury

TLRs

Major cell types

Exogenous ligands

Endogenous ligands

TLR1

Myeloid cells

T, B and NK cells, microglia, astrocytes

Bacterial triacyl-lipopeptide

 

TLR2

Myeloid cells, T cells, microglia, astrocytes, oligodendrocytes, neurons

Lipoproteins/lipopeptides, lipoteichoic acid, lipoarabinomannan, peptidoglycan,

glycoinositolphospholipids, glycolipids,

porins, zymosan, atypical lipopolysaccharide

Heat-shock proteins 60 and 70, Gp96,

Saturated fatty acids

TLR3

Epithelial cells, dendritic cells, microglia, astrocytes, oligodendrocytes, neurons

Double-stranded RNA

mRNA

TLR4

Myeloid cells, microglia, astrocytes, neurons

Lipopolysaccharide, paclitaxel,

respiratory syncytial virus fusion protein, mouse mammary tumor virus envelope proteins

Heat-shock proteins 60 and 70,

Gp96, Type III repeat extra domain A of fibronectin, oligosaccharides of hyaluronic acid, polysaccharide fragments of heparin sulfate, fibrinogen, high mobility group box 1, surfactant protein-A, β-defensin 2

TLR5

Myeloid cells, epithelial cells, microglia, astrocytes

Flagellin

 

TLR6

Myeloid cells, dendritic cells, microglia, astrocytes

Phenol-soluble modulin, diacyl lipopeptides, lipoteichoic acid, zymosan

 

TLR7

B cells, dendritic cells, microglia, astrocytes

Imidazoquinoline, loxoribine, bropirimine,

Single-stranded RNA

 

TLR8

Myeloid cells, microglia, astrocytes, neurons

Single-stranded RNA

 

TLR9

Epithelial and B cells, dendritic cells, microglia, astrocyte, neuron

Unmethylated CpG DNA

Chromatin-IgG complexes

TLR10

B cells, dendritic cells

Unknown, may interact with TLR2

 

TLR11

Myeloid cells, uroepithelial cells

Uropathogenic E. coli

 
  1. (Marsh et al., 2009b[13];Takeda and Akira, 2004[18]; Cristofaro and Opal, 2006[67]; Guo and Schluesener, 2007[68]; Tsan and Gao, 2004[69];)