Toll-like receptor TLR2, TLR3 and TLR4 expression in active IBD

Background: Chronic inflammation in inflammatory bowel disease (IBD) may result from exaggerated stimulation of the mucosal immune system by the endogenous luminal bacterial flora. Bacterial products are recognized by pattern recognition receptors (PRRs) like Toll-like receptors (TLRs), which are key regulators of the innate immune system. Aim: The aim of this study was to characterise the expression of TLR2, TLR3 and TLR4 in colonic biopsy samples taken from children with active IBD either freshly diagnosed (fd) or after relapse (r) on treatment and compared to controls. Methods: Colonic biopsy specimens were collected from 12 children [median (range): 13 (6–18) yr] with fdIBD and 23 children [15 (8–18) yr] with rIBD from macroscopically involved and noninvolved mucosa and 8 controls [median (range): 14 (6–16) yr]. TLR2, TLR3 and TLR4 mRNA expression were determined by real-time reverse transcription polymerase chain reaction (RT-PCR). Results: The TLR2 and TLR4 mRNA expression were significantly increased in the involved colonic mucosa of children with fdIBD and rIBD compared to controls (p<0,05). In the noninvolved mucosa of children with fdIBD and rIBD TLR2 and TLR4 mRNA expression were similar to controls (p=NS). We found higher TLR2 and TLR4 mRNA expression in the involved colonic mucosa of children with fdIBD and rIBD than in the noninvolved colonic mucosa of them (p<0,05). TLR2 and TLR4 mRNA expression in either involved or noninvolved mucosa were similar in children with fdIBD and rIBD (p=NS). The TLR3 mRNA expression did not changed significantly (p=NS).

Summary/Conclusion: Our results of increased expression of TLR2 and TLR4 mRNA in the inflammed mucosa of children with IBD confirm the hypothesis that innate immunity has an important effect in the pathogenesis of this disease.