The mechanism of action of probiotics

Purpose of review Probiotics are a heterogeneous group of nonpathologic bacteria that are functionally defined by their ability to allay inflammation when introduced into the inflamed intestine. The purpose of this review is to discuss recent data bearing on the possible mechanisms of action of these bacteria, with a particular focus on the relation of these mechanisms to the pathogenesis of inflammatory bowel disease, their main arena of use. Recent findings Studies of probiotic activity in recent years provide evidence that probiotics counter experimental and human gastrointestinal inflammation (human inflammatory bowel disease) by their effects on epithelial cell function, including epithelial cell barrier function, epithelial cytokine secretion, and their antibacterial effects relating to colonization of the epithelial layer. In addition, there is emerging evidence that probiotics induce regulatory T cells that act as a break on the effector T cells that would otherwise cause inflammation. Summary This review of probiotics and inflammatory bowel disease marshals support for the concept that administration of probiotics ameliorates inflammation by exerting positive effects on the epithelial cell dysfunction and mucosal immune system dysfunction that forms the basis of the inflammation.