The aim of the study: Previously we have found higher TLR2 and TLR4 mRNA expression and protein levels in the duodenal mucosa of children with untreated CD than in controls. Our aim was to characterise the expression of TLR2, TLR3 and TLR4 in duodenal biopsy samples taken from children with treated CD compared to untreated CD and controls.

Methods: Duodenal biopsy specimens were collected from 9 children with treated CD [median age (range): 6 (3-14)], 16 children with untreated CD [median age (range): 9 (4-15)] and 10 [median age (range): 10 (4-15)] controls. The mRNA expression of TLR2, TLR3 and TLR4 was determined by semi-quantitative reverse transcription- polymerase chain reaction (RT-PCR). Protein level of TLRs was determined by Western blot.

Results: We found even higher TLR2 and TLR4 mRNA levels in the duodenal mucosa of children with treated CD than in untreated CD and controls (p<0.001 for all comparisons). TLR3 mRNA expression was also increased in the duodenal mucosa of children with treated CD compared to untreated CD and controls (p<0.001 for both comparisons). In the duodenal mucosa of children with treated CD, TLR2 protein level was fourfold- and TLR4 protein level was threefold higher than in untreated CD (p<0.001). We were able to detect TLR3 protein only in biopsy specimens of treated CD patients.

Summary: Increased expression of TLR2 and TLR4 was found in children with coeliac disease.

Conclusions: Our results of increased expression of TLR2 and TLR4 even in treated CD may indicate the primary role of these pattern recognition receptors in the pathogenesis of CD.