Purpose of review: Chronic inflammatory bowel diseases appear to result from inappropriate immune responses driven by apparently normal intestinal microflora in genetically susceptible hosts. This review focuses on recently described mechanisms balancing toll-like receptor and nucleotide-binding-oligomerization domain activation in the face of ubiquitous enteric flora.
Recent findings: Toll-like receptor and nucleotide-binding-oligomerization domain signaling plays an integral role in the close collaboration between the intestinal epithelial cell monolayer and adjacent mucosal immune cells. Pathways activated by functional cytosolic nucleotide-binding-oligomerization domain proteins appear to interact with those mediated by membrane-associated toll-like receptors in the innate and adaptive immune defense against intra-and extracellular pathogens. Nucleotide-binding-oligomerization domain-mediated signaling may also control toll-like receptor-induced proinflammatory pathways.
Summary: Intersections between toll-like receptor and nucleotide-binding-oligomerization domain pathways may exist to refine the host immune response to pathogens and prevent undesired immune stimulation driven by the intestinal microbiota. Deficient toll-like receptor and nucleotide-binding-oligomerization domain function due to genetic variability is associated with an increased susceptibility to the development of inflammatory bowel disease.