Table 1.
Types of TLRs described as associated with CD and UC. CS: cell surface; IC: intracellular; Mø: Monocytes/macrophages; B: B lymphocytes; MCs: mast cells; N: neutrophils; DCs: dendritic cells; IECs: intestinal epithelial cells. Data reported in table were collected from [45,46,47].
| TLR | Adapter | Compartments | Ligands | Cell Types | Main Alterations in IBD |
|---|---|---|---|---|---|
| TLR1 | MyD88/TRIAP | CS | Di- and tri-acylated lipopeptides | Mø, B, MCs | No variation in IBD |
| TLR2 | MyD88/TRIAP | CS | Bacterial lipoproteins or lipopeptides | Mø, B, MCs | Increased in active UC |
| TLR3 | TRIF | IC | Double-stranded RNA (viral infection) | Mø, B, MCs, N, Myeloid DCs, IECs | Increased in active UC and CD |
| TLR4 | MyD88/TRIAP, TRIF/TRAM | CS | LPS, free fatty acids | Mø, B, MCs, N, Myeloid DCs, IECs | Increased in UC and CD |
| TLR5 | MyD88 | CS | Bacterial flagellins | Mø, Myeloid DCs, IECs | Decreased in CD |
| TLR6 | MyD88/TRAF6 and NF-κB pathway | CS | Di- and tri-acylated lipopeptides | Mø, B, MCs | Increased in UC |
| TLR7 | MyD88 | IC/Endosomal | Single stranded RNA (viral inflammation) | Mø | Increased in UC |
| TLR8 | MyD88 | IC/endosomal | RNA degradation products specific to microorganism (GU-rich single stranded RNA) | Mø, DCs | Increased in UC |
| TLR9 | MyD88/TRAF6 | IC | Nucleid acid | Mø, B, plasmacytoid DCs | Increased in UC |