The Mechanism of Action of Probiotics.
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.
In recent years it has become evident that while the complex array of organisms comprising our gastrointestinal microflora lack the invasive characteristics of pathogens, they nevertheless have some capacity to penetrate the epithelial barrier and thereby to evoke mucosal immune responses. For the most part the latter are tolerogenic responses that allow the microflora to reside in harmony with the host immune system. In certain individuals, however, such as those with inflammatory bowel diseases, this balance is upset and the organisms in the microflora induce immune responses that lead to inflammation and disease. In the attempt to right this imbalance, investigators have sought commensal organisms that when introduced into a gastrointestinal inflammatory milieu, calm or even eliminate the inflammation. Organisms with such characteristics, termed probiotics, have in fact been identified, although at the moment their ability to quell gut inflammation appears to be quite limited. In the following review we will consider the mechanisms by which these organisms exert their therapeutic effects; in doing so we hope to gain new insight into how the normal microflora interacts with the mucosal immune system to maintain homeostasis.
Abstract and Introduction
Abstract
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.
Introduction
In recent years it has become evident that while the complex array of organisms comprising our gastrointestinal microflora lack the invasive characteristics of pathogens, they nevertheless have some capacity to penetrate the epithelial barrier and thereby to evoke mucosal immune responses. For the most part the latter are tolerogenic responses that allow the microflora to reside in harmony with the host immune system. In certain individuals, however, such as those with inflammatory bowel diseases, this balance is upset and the organisms in the microflora induce immune responses that lead to inflammation and disease. In the attempt to right this imbalance, investigators have sought commensal organisms that when introduced into a gastrointestinal inflammatory milieu, calm or even eliminate the inflammation. Organisms with such characteristics, termed probiotics, have in fact been identified, although at the moment their ability to quell gut inflammation appears to be quite limited. In the following review we will consider the mechanisms by which these organisms exert their therapeutic effects; in doing so we hope to gain new insight into how the normal microflora interacts with the mucosal immune system to maintain homeostasis.
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