Microbes and their products--physiological effects upon mammalian mucosa.

A dynamic array of interactions occurs between pathogens and host mucosal surfaces. The signature molecules unique to microbial pathogens allow the mammalian immune system to recognize them as non-self. This recognition, mediated by the toll-like receptor proteins, results in innate immune responses targeted against the invading organism. Pathogens also elaborate a variety of proteins that actively engage host signaling pathways and subvert them to facilitate their growth and dispersal. These interactions, developed over a long evolutionary period, have been specialized to exquisite detail. These proteins and toxins are either secreted into the medium or directly delivered into host cells by specialized secretion systems. An array of host function alterations is mediated by microbial pathogens including inflammatory responses, secretory responses, alteration of host cytoskeleton, disruption of epithelial tight junctions and apoptosis. The signaling axes involved in these interactions are potential targets for therapeutic strategies against infectious microbes.