Battling enteroinvasive bacteria:: Nod1 comes to the rescue

Recognition of pathogenic bacteria by mammalian hosts is largely mediated by membrane-bound Toll-like receptors (TLRs). Recently, a family of cytosolic proteins, termed NODs, with homology to plant disease-resistance gene products has been implicated in sensing microbes within the cytosol. The role of NOD family members in host defense is largely unknown. However, a recent report revealed that Nod1 is a crucial sensor for certain enteroinvasive bacteria that avoid TLR signaling. This finding suggests that Nod 1 plays an important role in the initial recognition of pathogenic bacteria at epithelial surfaces, such as the gut,where innate immune responses to commensal bacteria must be avoided.