Table 1. Human Toll-like Receptor Expression and Their Ligands.
| TLRs | expressed on human | exogenous ligands | endogenous liganda |
|---|---|---|---|
| TLR1 | endothelial cells (ECs); Vascular smooth muscle cells(VSMCs); monocyte; macrophages; B cells; neutrophils; NK cells; platelets | cooperate with TLR2 to recognize triacyl lipopeptides | NA |
| TLR2 | ECs; VSMCs; fibroblasts; monocyte; dendritic cells (DCs); NK cells; platelets | peptidoglycans; lipoproteins; LPS; beta-glucan | human β-defensins; acute serum amyloid A; histones; cooperate with TLR2 to recognize HMGB1; HSPs; ECM |
| TLR3 | ECs; VSMCs; macrophages; T lymphocytes; DCs | dsRNA; ssRNA | NA |
| TLR4 | ECs; VSMCs; macrophages; mast cells; B and T lymphocytes; platelets | LPS; glycoproteins; fibronectin | HSP60; HSP70; HMGB1, fibronectin; hyaluronic acid; biglycan; oxLDL; mmLDL, fetuin-A; Ang II; serum amyloid A; histones; S100 proteins |
| TLR5 | ECs; VSMCs; monocytes; macrophages; DCs; neutrophils; T cells | flagellin | NA |
| TLR6 | ECs; VSMCs; macrophages; B cells; platelets | cooperate with TLR2 to recognize diacyl lipopeptides | cooperate with TLR2 to recognize HMGB1; HSPs; ECM |
| TLR7 | ECs; VSMCs; DCs; monocytes; macrophages; T cells; B cells; platelets | ssRNA | guanosine and its modified derivatives; siRNA |
| TLR8 | Monocytes; Macrophages; DCs; Neutrophils | ssRNA | siRNA |
| TLR9 | ECs; VSMCs; macrophages; plasmacytoid DCs; T cells; B cells; platelets | CpG DNA | histones; mitochondrial DNA |
| TLR10 | monocytes; neutrophils; plasmacytoid DCs; B cells | unknown | NA |
a
NA: not available.