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Interleukin (IL) 17-secreting CD4+ helper T cells (Th17 cells) are essential for host defense at mucosal surfaces, and Th17 cell dysregulation can result in autoimmunity. Exposure to microbial products, such as bacterial LPS, can affect the ability of dendritic cells (DCs) to polarize Th17 cells. Acyloxyacyl hydrolase (AOAH) is a mammalian enzyme expressed by antigen (Ag)-presenting cells that deacylates and thereby inactivates LPS in host tissues. We hypothesized that inactivation of intestinal microbiota-derived LPS by AOAH influences the ability of DCs to polarize and generate Th17 effector cells. We found that LPS-containing Gram-negative microbiota augmented the differentiation of Ag-specific Th17 cells, and identified a colonic DC subset (CD103+CD11b+ALDH−) displaying a unique capacity to both express AOAH and polarize Th17 cells. Compared with WT, these Aoah−/− colonic DCs produce less IL-6, resulting in diminished Ag-specific Th17 polarization and increased regulatory T-cell induction in vitro. Oral administration of LPS led to reduced IL-6 production from CD103+CD11b+ALDH− colonic DCs in Aoah−/− mice compared with Aoah+/+ mice, resulting in an abrogated Ag-specific Th17 response in the colon after mucosal immunization that could be rescued by systemic delivery of recombinant IL-6. These data identify the ability of AOAH to modulate microbiota signals that drive Th17 polarization and influence mucosal T-cell immunity, and suggest that host pathways to handle microbiota-derived products may be targeted to modulate Th17 responses in the context of inflammatory disorders or infection at mucosal surfaces. [ABSTRACT FROM AUTHOR]

Activation of Toll-like receptors (TLR) contributes to the initiation and maintenance of chronic inflammation in autoimmune diseases, yet repeated exposure to a TLR agonist can induce hyporesponsiveness to subsequent TLR stimulation. Here, we used a synthetic TLR7 agonist, 9-benzyl-8-hydroxy-2-(2-methoxyethoxy) adenine (SM360320, 1V136) to study TLR7 induced attenuation of inflammatory responses and its application to autoimmune diseases. Repeated low dose administration of this TLR7 agonist induced hyporesponsiveness or tolerance to TLR2, -7, and -9 activators and limited the course of neural inflammation in an experimental allergic encephalomyelitis model. The hyporesponsiveness did not depend on T or B lymphocytes, but did require bone marrow derived cells. In addition, TLR7 tolerance reduced inflammation in a passive antibody mediated arthritis model. TLR7 tolerance did not cause global immunosuppression, because susceptibility to Listeria monocytogenes infection was not altered. The mechanism of TLR7 tolerance involved the up-regulation of 2 inhibitors of TLR signaling: Interleukin 1 Receptor Associated Kinase (IRAK) M, and Src homology 2 domain-containing inositol polyphosphate phosphatase (SHIP)-1. These findings suggest that induction of TLR7 tolerance might be a new therapeutic approach to subdue inflammation in autoimmune diseases. [ABSTRACT FROM AUTHOR]

Mechanisms underlying modern increases in prevalence of human inflammatory diseases remain unclear. The hygiene hypothesis postulates that decreased microbial exposure has, in part, driven this immune dysregulation. However, dietary fatty acids also influence immunity, partially through modulation of responses to microbes. Prior reports have described the direct effects of high-fat diets on the gut microbiome and inflammation, and some have additionally shown metabolic consequences for offspring. Our study sought to expand on these previous observations to identify the effects of parental diet on offspring immunity using mouse models to provide insights into challenging aspects of human health. To test the hypothesis that parental dietary fat consumption during gestation and lactation influences offspring immunity, we compared pups of mice fed either a Western diet (WD) fatty acid profile or a standard low-fat diet. All pups were weaned onto the control diet to specifically test the effects of early developmental fat exposure on immune development. Pups from WD breeders were not obese or diabetic, but still had worse outcomes in models of infection, autoimmunity, and allergic sensitization. They had heightened colonic inflammatory responses, with increased circulating bacterial LPS and muted systemic LPS responsiveness. These deleterious impacts of the WD were associated with alterations of the offspring gut microbiome. These results indicate that parental fat consumption can leave a "lard legacy" impacting offspring immunity and suggest inheritable microbiota may contribute to the modern patterns of human health and disease. [ABSTRACT FROM AUTHOR]