Gut microbiota and lipopolysaccharide content of the diet influence development of regulatory T cells: studies in germ-free mice

Abstract

Background: Mammals are essentially born germ-free but the epithelial surfaces are promptly colonized by astounding numbers of bacteria soon after birth. The most extensive microbial community is harbored by the distal intestine. The gut microbiota outnumber ~10 times the total number of our somatic and germ cells. The host-microbiota relationship has evolved to become mutually beneficial. Studies in germ-free mice have shown that gut microbiota play a crucial role in the development of the immune system. The principal aim of the present study was to elucidate whether the presence of gut microbiota and the quality of a sterile diet containing various amounts of bacterial contaminants, measured by lipopolysaccharide (LPS) content, can influence maturation of the immune system in gnotobiotic mice.

The role of gut microbiota (commensal bacteria) and the mucosal barrier in the pathogenesis of inflammatory and autoimmune diseases and cancer: contribution of germ-free and gnotobiotic animal models of human diseases

“…35,40,42,43 In the early postnatal period, components of the normal microbiota induce a transient physiological inflammatory response in the gut associated with enlargement of the mucosal-associated lymphatic tissue and increases in its cellularity. 39,45 The effect of microbial colonization on innate immune cells has been documented in our studies on the development of phagocytes, dendritic cells and intestinal epithelial cells. 24,46 Interestingly, the Tcell receptor repertoire is also influenced by colonization with microorganisms.…”

“…An important finding was that the development of regulatory (CD4 1 FoxP3 1 ) T lymphocytes depends on the presence of the microbiota and bacterial components in the diet: germ-free mice on a diet containing small amounts of lipopolysaccharide had fewer regulatory T lymphocytes. 45 Interestingly, the microbial colonization of germ-free mice also speeds up the biochemical maturation of enterocytes, resulting in a shift in the specific activities of brush-border enzymes nearly to the extent found in conventional mice. 48 Moreover, a similar introduction of microorganisms alters the synthesis of sugar chains in membrane-associated glycoproteins, which could influence the gut barrier function.…”

Regulation of immunity and disease resistance by commensal microbes and chromatin modifications during zebrafish development

“…For example, it has been noticed that intestines of GF mice can initiate but cannot complete their differentiation when particular associations between host and microbes are lacking (4). Using a similar model, Hrncir et al (27) found that bacterial LPS, which is present as a contaminant in mouse food, is needed to develop a healthy phenotype. Unfortunately, available model species are scarce, and most findings under GF conditions are derived largely from a few mammalian species, mainly rodents (28) and swine (29).…”

Colorectal carcinoma: Importance of colonic environment for anti-cancer response and systemic immunity

“…Still, from an immunological viewpoint, the absence of chronic pro-inflammatory environment, the reduced regulatory network in the lamina propria, the much lower amount of molecules to be tolerated, deriving from the bacterial metabolisms of alimentary products and from the same bacteria, can lead to a more naïve and plastic immunity (Vannucci et al, 2008;Hrncir et al, 2008). This should be indicated by the relatively lower proportion of T-lymphocytes versus the innate immunity cells in healthy conditions, the hypoplastic mesenteric lymph nodes, but also by a more valid immune reactivity against transformed cells, as described above.…”