Expression of Toll-like receptors in the intestinal mucosa of patients with inflammatory bowel disease.

Inflammatory bowel disease (IBD) consists of Crohn's disease, which involves not only the large intestine but also the small intestine, and ulcerative colitis, which only involves the large intestine. The dysregulation of innate and adaptive intestinal immune responses to bacterial microbiota is believed to be highly involved in the pathogenesis of IBD. Toll-like receptors (TLRs) play a key role in microbial recognition in innate immunity and control the adaptive immune responses. Among the TLRs, TLR2 recognizes bacterial lipoprotein and peptidoglycan, whereas TLR4 and its coreceptor, CD14, recognize lipopolysaccharide. The expression levels of TLR2 or TLR4 have been shown to be limited in the intestine of healthy volunteers, suggesting a minimalization of the recognition of microbiota in the intestinal lumen. The paper under evaluation highlighted the expression levels of TLR2, TLR4 and CD14 in the terminal ileum, cecum and rectum of IBD patients (19 Crohn's disease and 20 ulcerative colitis patients) and of 20 healthy volunteers. The authors suggested that the dysregulation of TLR2, TLR4 and CD14 expression in different parts of the intestinal mucosa might, therefore, play a crucial role in the pathogenesis of IBD.