The gut microbiome and the immune system

Abstract

The human body contains trillions of microbes which generally live in symbiosis with the host. The interaction of the gut microbiome with elements of the host immune system has far-reaching effects in the development of normal gut and systemic immune responses. Disturbances to this intricate relationship may be responsible for a multitude of gastrointestinal and systemic immune mediated diseases. This review describes the development of the gut microbiome and its interaction with host immune cells in both health and disease states.

The Gut-Brain Axis and the Microbiome in Anxiety Disorders, Post-Traumatic Stress Disorder and Obsessive-Compulsive Disorder

“…with the vagus nerve, to send signals to the central nervous system (CNS), and in a bidirectional fashion, the CNS can send signals to the gut to modulate the composition and function of the microbiome [ 9 , 25 ]. There is constant communication among the mucosal, peripheral and central immune systems and the gut microbiome [ 8 , 27 ], and the endocrine system also communicates bidirectionally with the gut microbiome, with the hypothalamic-pituitary-adrenal (HPA) axis thought to play a major role [ 7 ]. In chronic stress situations, the gut epithelial layer may become more permeable, resulting in increased movement of endotoxins from inside the gut to the outside, leading to a low-grade inflammation characteristic of a number of mood and anxiety disorders [ 2 , 10 , 28 ].…”

Microbiome Dynamics: A Paradigm Shift in Combatting Infectious Diseases

“…However, an imbalance in the gut microbiome can lead to impaired immune function and the development of conditions such as diabetes, obesity, and inflammatory bowel disease (IBD). These conditions, in turn, can further impact the health of the microbiome [80,81]. Changes in microbiome composition and function associated with these conditions can impair immune responses and mucosal barrier functions, potentially increasing vulnerability to pathogens.…”

A narrative review on the use of probiotics in several diseases. Evidence and perspectives

“…Generally, an eubiotic gut microbiota and probiotics positively affect both host’s innate and adaptive immunity ( 12 ); concerning innate immunity, gut microbiota acts both locally and systemically, by influencing the development and function of antigen presenting cells (APCs), neutrophils and other innate cell types ( 12 ). Moreover, it has been reported the ability of gut microbiota and of some probiotics to affect innate immunity outside the gut milieu, for example by promoting the attenuation of inflammation processes at local levels ( 13 , 14 ).…”

“…Moreover, it has been reported the ability of gut microbiota and of some probiotics to affect innate immunity outside the gut milieu, for example by promoting the attenuation of inflammation processes at local levels ( 13 , 14 ). There is also a role on adaptive immunity, due to the effect in the development of the most important subtypes of CD4 + T cells (or helper T cells, which are lymphocytes coordinating the response to diseases), that is Th1, Th2, Th17 and T reg ( 12 , 15 ). In addition to T cells, an eubiotic gut microbiota could influence B cell maturation and immunoglobulin production ( 16 ).…”

“…SCFA are produced through the fermentation of non-digestible carbohydrates and amino acids in the colon and play a major role in maintaining the barrier function of gut ( 18 ). They are absorbed by the colonocytes and used as fuel for the colonic mucosal epithelial cells ( 19 ), but at the same time they directly act on gut mucosa; for example, butyrate contributes to reduce oxidative stress, thus stabilizing gut mucosa and reducing the translocation of LPS (Lipopolysaccharide) ( 12 ). Also, bile salts are essential for immunity in a bidirectional crosstalk between host and microbiota.…”