Intestinal Microbiota as Modulators of the Immune System and Neuroimmune System: Impact on the Host Health and Homeostasis (original) (raw)

Intestinal Microbiota Influences Non-intestinal Related Autoimmune Diseases

Frontiers in Microbiology, 2018

The human body is colonized by millions of microorganisms named microbiota that interact with our tissues in a cooperative and non-pathogenic manner. These microorganisms are present in the skin, gut, nasal, oral cavities, and genital tract. In fact, it has been described that the microbiota contributes to balancing the immune system to maintain host homeostasis. The gut is a vital organ where microbiota can influence and determine the function of cells of the immune system and contributes to preserve the wellbeing of the individual. Several articles have emphasized the connection between intestinal autoimmune diseases, such as Crohn's disease with dysbiosis or an imbalance in the microbiota composition in the gut. However, little is known about the role of the microbiota in autoimmune pathologies affecting other tissues than the intestine. This article focuses on what is known about the role that gut microbiota can play in the pathogenesis of non-intestinal autoimmune diseases, such as Grave's diseases, multiple sclerosis, type-1 diabetes, systemic lupus erythematosus, psoriasis, schizophrenia, and autism spectrum disorders. Furthermore, we discuss as to how metabolites derived from bacteria could be used as potential therapies for non-intestinal autoimmune diseases.

The immune system and the gut microbiota: friends or foes?

Nature Reviews Immunology, 2010

The mammalian intestine is home to a complex community of trillions of bacteria that are engaged in a dynamic interaction with the host immune system. Determining the principles that govern host-microbiota relationships is the focus of intense research. Here, we describe how the intestinal microbiota is able to influence the balance between pro-inflammatory and regulatory responses and shape the host's immune system. We suggest that improving our understanding of the intestinal microbiota has therapeutic implications, not only for intestinal immunopathologies but also for systemic immune diseases.

Gut Microbiota, Dysbiosis and Immune System; A Brief Review

2019

The gut Microbiota is the large population of microorganisms residing in the human gastrointestinal tract. The gut Microbiota constantly interacts with the various host organs and systems. While there are many protective functions due to the gut Microbiota, changes in the composition and function of the Microbiota, which is defined as dysbiosis, has been shown in several diseased conditions. The gut Microbiota affect the immune system. While normal gut Microbiota are essential for existence of a normal immune system, dysbiosis can result in deviation of immune responses. In this article, we will talked the effects of the gut Microbiota on different elements of immune system.

Gut Microbiota and Its Pathophysiology in Disease Paradigms

Digestive Diseases, 2011

The gut flora carries out important functions for human health, although most of them are still unknown, and an alteration of any of them, due to a condition of dysbiosis, can lead to relevant pathological implications. Commensal bacteria in the gut are essential for the preservation of the integrity of the mucosal barrier function and an alteration in the anatomic functional integrity of this barrier has been implicated in the pathophysiologic process of different diseases. The gut microflora plays a role in modulating the intestinal immune system; in fact, it is essential for the maturation of gut-associated lymphatic tissue, the secretion of IgA and the production of antimicrobial peptides. The enteric flora represents a potent bioreactor which controls several metabolic functions, even if most of them are still unknown. The main metabolic functions are represented by the fermentation of indigestible food substances into simple sugars, absorbable nutrients, and short-chain fatty ...

Intestinal microbiota and immune function in the pathogenesis of irritable bowel syndrome

AJP: Gastrointestinal and Liver Physiology, 2013

Intestinal microbiota and immune function in the pathogenesis of irritable bowel syndrome. ogy of irritable bowel syndrome (IBS) is believed to involve alterations in the brain-gut axis; however, the etiological triggers and mechanisms by which these changes lead to symptoms of IBS remain poorly understood. Although IBS is often considered a condition without an identified "organic" etiology, emerging evidence suggests that alterations in the gastrointestinal microbiota and altered immune function may play a role in the pathogenesis of the disorder. These recent data suggest a plausible model in which changes in the intestinal microbiota and activation of the enteric immune system may impinge upon the brain-gut axis, causing the alterations in gastrointestinal function and the clinical symptoms observed in patients with IBS. This review summarizes the current evidence for altered intestinal microbiota and immune function in IBS. It discusses the potential etiological role of these factors, suggests an updated conceptual model for the pathogenesis of the disorder, and identifies areas for future research.

Human Colon Microbiota and Mucosal Immune System

Applied Medical Research, 2015

Number of microorganisms located in our microbiota is estimated to be about 10 times more than the host cells. Microbiota is located mostly in the gastrointestinal tract and it consists of a high number of mutualistic and commensal microorganisms. Microorganisms in this tract have a particular prominent localization in terminal ileum and colon. Colon microbiota is considered the most important component of the human mucosal immune system. Mucosal immune system also participates in immune defense of eyes, nasal mucosa, genitourinary and respiratory system. Composition, organization and concentration of colon microbiota are thought to be directly connected with pathogenesis of diseases such as Crohn's disease, Ulcerative Colitis, Irritable Bowel Syndrome, Coeliac disease, food allergies and colon cancer. In this article we will discuss about the general characteristics of human colon microbiota and its relationship with etiopathology diseases. The importance of its role in the pathogenesis of diseases and contributions to immune system has recently begun to be understood. Further researches will guide us to understand the etiopathology of these diseases much better and lead us to reveal more effective outcomes.

The putative role of the intestinal microbiota in the irritable bowel syndrome

Digestive and Liver Disease, 2009

The irritable bowel syndrome (IBS) is a chronic abdominal symptom complex that is heterogeneous in terms of its clinical presentation and underlying pathophysiology and pathogenesis. It is now established that enteric infection can trigger the syndrome in at least a subset of patients. In addition, there is growing evidence of low grade inflammation and immune activation in the distal bowel of some IBS patients. These observations now prompt the question as to what maintains gut dysfunction in these patients. The intestinal microbiota influences a broad array of host organs that include the gut and the brain, and is an important determinant of normal function in these systems. Disruption of the delicate balance between the host and its intestinal microbiota (termed dysbiosis) results in changes in the mucosal immune system that range from overt inflammation as seen in Crohn's Disease, to low grade inflammation without tissue injury, as seen in a subset of IBS patients. Under experimental conditions, disruption of the microbiota also produces changes in gut sensory-motor function and immune activity. Thus, dysbiosis induced by infection, dietary change or drugs such as antibiotics could produce low grade inflammation and chronic gut dysfunction, reminiscent of that seen in IBS. Fluctuations in gut physiology destabilize the habitat of commensal bacteria and provide a basis for chronic dysbiosis. Recent observations in animal models that changes in gut flora influence behavior provide a basis for a novel unifying hypothesis that accommodates both gut dysfunction and behavioral changes that characterize many IBS patients. This hypothesis states that dysbiosis exists in at least a subset of IBS patients, as a result of infection, dietary change or drugs and contributes to gut inflammatory and functional change in addition to psychiatric co-morbidity.

Microbiome, Immunomodulation, and the Neuronal System

Neurotherapeutics, 2018

Vertebrates harbor both symbiotic and pathogenic bacteria on the body and various mucosal surfaces. Of these surfaces, the intestine has the most diverse composition. This composition is dependent upon various environmental and genetic factors, with diet exerting the maximum influence. Significant roles of the intestinal bacteria are to stimulate the development of a competent mucosal immune system and to maintain tolerance within the intestine. One manner in which this is achieved is by the establishment of epithelial integrity by microbiota found in healthy individuals (healthy microbiota); however, in the case of a disrupted intestinal microbiome (dysbiosis), which can be caused by various conditions, the epithelial integrity is compromised. This decreased epithelial integrity can then lead to luminal products crossing the barrier, generating a systemic proinflammatory response. In addition to epithelial integrity, healthy intestinal commensals metabolize indigestible dietary substrates and produce short-chain fatty acids, which are bacterial metabolites that are essential for colonic health and regulating the function of the intestinal immune system. Intestinal commensals are also capable of producing neuroactive molecules and neurotransmitters that can affect the function of the vagus nerve. The observations that intestinal dysbiosis is associated with different diseases of the nervous system, suggests that cross-talk occurs amongst the gut, the nervous system, and the immune system.

The Role of Diet and Gut Microbiota in Regulating Gastrointestinal and Inflammatory Disease

Frontiers in Immunology

Diet is an important lifestyle factor that is known to contribute in the development of human disease. It is well established that poor diet plays an active role in exacerbating metabolic diseases, such as obesity, diabetes and hypertension. Our understanding of how the immune system drives chronic inflammation and disease pathogenesis has evolved in recent years. However, the contribution of dietary factors to inflammatory conditions such as inflammatory bowel disease, multiple sclerosis and arthritis remain poorly defined. A western diet has been associated as pro-inflammatory, in contrast to traditional dietary patterns that are associated as being anti-inflammatory. This may be due to direct effects of nutrients on immune cell function. Diet may also affect the composition and function of gut microbiota, which consequently affects immunity. In animal models of inflammatory disease, diet may modulate inflammation in the gastrointestinal tract and in other peripheral sites. Despit...