Understanding the Dialogue: the Microbial–Host Interaction
The mammalian gastrointestinal tract is much more complex than previously appreciated. A single layer of epithelial cells covers the entire gastrointestinal tract, so providing the largest interface with the environment. The gut epithelium is a sensor of the luminal environment, not only controlling digestive, absorptive, and secretory functions, but also relaying information to the mucosal immune, vascular and nervous systems. These functions involve a complex array of pattern recognition receptors (PRRs) and cell types that elaborate growth factors, cytokines, and extracellular matrix proteins. Moreover, enteric microbes may hijack PRR-activated pathways as part of their pathogenic arsenal through ‘host mimicry’. Understanding the cross-talk between enteric microbiota and the host under both physiological and pathological circumstances may provide key information on the pathogenesis of local as well as systemic diseases. This knowledge may potentially lead to the identification of novel therapeutic strategies for the treatment of these disorders.