Review Article
Innate Immunity and Neuroinflammation
Table 2
Exogenous and endogenous ligands of toll-like receptors.
| Ligand | TLR | Implications/comments | References |
| Lipopolysaccharide | TLR4 | Recognition of Gram (−) bacteria | [117] | Triacylated lipopeptides | TLR1 and TLR2 | Recognition of Gram (−) bacteria and mycobacteria | [118] | Diacylated lipopeptides | TLR2 and TLR6 | Recognition of Gram (+) bacteria and mycoplasma | [119, 120] | Lipoteichoic acid | TLR2 | Recognition of Gram (+) bacteria | [121] | Zymosan | TLR2 | Recognition of fungi | [122] | Double-stranded RNA | TLR3 | Recognition of virus | [123] | Single-stranded RNA | TLR7 and TLR8 | Recognition of virus | [124, 125] | Flagellin | TLR5 | Recognition of Gram (−) bacteria | [126] | Unmethylated CpG DNA | TLR9 | Recognition of bacteria and virus | [127, 128] | β-amyloid | TLR2; TLR4; TLR4 and TLR6 | Neuroinflammation in Alzheimer’s disease | [95, 96, 129, 130] | Mitochondrial DNA | TLR9 | Pathogenesis of myocarditis and heart failure | [128] | Lung surfactant protein-A and -D | TLR4 TLR2 | Innate immune component of lung. Act as opsonin and macrophage activator. Physiological implications of excessive activation by TLR is not known | [131–133] | Tenascin-C | TLR4 | Maintenance and pathogenesis of inflammation in rheumatoid arthritis | [134, 135] | Fibrinogen | TLR4 | Present normally in serum and activation has been implicated in rheumatoid arthritis and atherosclerosis | [136, 137] | Oxidised low-density lipoprotein | TLR4 | Pathogenesis of atherosclerosis | [95] | MicroRNA let-7 | TLR7 | Pathogenesis of neurodegeneration | [138] |
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