Exploring the immunomodulatory potential of microbial-associated molecular patterns derived from the enteric bacterial microbiota

The human intestinal lumen represents one of the most densely populated microbial niches in the
biological world and, as a result, the intestinal innate immune system exists in a constant state of
stimulation. A key component in the innate defence system is the intestinal epithelial layer, which
not only acts as a physical barrier, but also as an immune sensor. The expression of pattern
recognition receptors, such as Toll-like receptors, in epithelial cells allows innate recognition of a
wide range of highly conserved bacterial moieties, termed microbial-associated molecular
patterns (MAMPs), from both pathogenic and non-pathogenic bacteria. To date, studies of
epithelial immunity have largely concentrated on inflammatory pathogenic antigens; however, this
review discusses the major types of MAMPs likely to be produced by the enteric bacterial
microbiota and, using data from in vitro studies, animal model systems and clinical observations,
speculates on their immunomodulatory potential.