Intestinal regulatory T cell induction by ß-elemene alleviates the formation of fat tissue-related inflammation.

The role of the intestinal immune system in the inhibition of fat tissue-related inflammation by dietary material is yet to be elucidated. Oral administration of ß-elemene, contained in various foodstuffs, downregulated expressions of inflammatory cytokines and increased Foxp3+CD4+ T cells in adipose tissue of obese mice. However, ß-elemene did not affect the inflammatory response of adipose tissue in vitro, suggesting that the inhibition observed in vivo was not due to direct interactions of adipose tissue with ß-elemene. Instead, ß-elemene increased Foxp3+CD4+ T cell population enhancing gene expressions of transforming growth factor ß 1, retinaldehyde dehydrogenase 2, integrin αvß8, and interleukin-10 in intestinal dendritic cells (DCs) in vivo and in vitro. Taken together, this study suggested the therapeutic effects of ß-elemene on treating experimental obesity-induced chronic inflammation by adjusting the balance of immune cell populations in fat tissue through the generation of regulatory T cells in the intestinal immune system by modulating DC function.

Age-Dependent Decrease in the Induction of Regulatory T Cells Is Associated With Decreased Expression of RALDH2 in Mesenteric Lymph Node Dendritic Cells.

A decline in immune function with aging has been reported. Regulatory T cell (Treg) induction is known to decrease with age, and elucidating the underlying mechanism is important for preventing age-related diseases due to age-related chronic inflammation. In the intestine, dendritic cells (DCs) play an important role in inducing Tregs specific to oral antigens, and they efficiently induce Tregs via production of retinoic acid (RA), a vitamin A metabolite, catalyzed by the enzyme retinaldehyde dehydrogenase 2 (RALDH2). We have previously reported that in the mesenteric lymph node (MLN), a secondary lymphoid tissue in which immune responses to oral antigens are induced, four DC subsets express different levels of CD11b, CD103, and PD-L1, and we have reported that the CD11b-CD103+PD-L1high subset expresses the highest levels of the RALDH2 gene and induces Tregs in vitro. We examined Treg induction in young and aged mice using a Treg induction model by administering a food antigen, and we found that antigen-specific Treg induction was decreased in aged mice. We further investigated the MLN DCs, and a significant decrease in RALDH2 gene expression was observed in MLN DCs from aged mice. As factors, we found that the proportion of the CD11b-CD103+PD-L1high subset was decreased in aged mice compared with that in young mice and that RALDH enzyme activity was decreased in the CD11b-CD103+PD-L1high and CD11b+CD103+PD-L1high subsets. Furthermore, analysis of the methylation of the RALDH2 gene promoter region revealed that CpG motifs were more methylated in the MLN DCs of aged mice, suggesting that RALDH2 expression was suppressed by epigenetic changes. Finally, we found that RA treatment tended to increase Treg induction. These results suggest that the regulation of RA production may be involved in the age-related decrease in antigen-specific Treg induction.

Critical role of intestinal interleukin-4 modulating regulatory T cells for desensitization, tolerance, and inflammation of food allergy.

BACKGROUND AND OBJECTIVE: The mechanism inducing either inflammation or tolerance to orally administered food allergens remains unclear. To investigate this we analyzed mouse models of food allergy (OVA23-3) and tolerance (DO11.10 [D10]), both of which express ovalbumin (OVA)-specific T-cell receptors. METHODS: OVA23-3, recombination activating gene (RAG)-2-deficient OVA23-3 (R23-3), D10, and RAG-2-deficient D10 (RD10) mice consumed a diet containing egg white (EW diet) for 2-28 days. Interleukin (IL)-4 production by CD4+ T cells was measured as a causative factor of enteropathy, and anti-IL-4 antibody was used to reveal the role of Foxp3+ OVA-specific Tregs (aiTreg) in this process. RESULTS: Unlike OVA23-3 and R23-3 mice, D10 and RD10 mice did not develop enteropathy and weight loss on the EW diet. On days 7-10, in EW-fed D10 and RD10 mice, splenic CD4+ T cells produced significantly more IL-4 than did those in the mesenteric lymph nodes (MLNs); this is in contrast to the excessive IL-4 response in the MLNs of EW-fed OVA23-3 and R23-3 mice. EW-fed R23-3 mice had few aiTregs, whereas EW-fed RD10 mice had them in both tissues. Intravenous injections of anti-IL-4 antibody recovered the percentage of aiTregs in the MLNs of R23-3 mice. On day 28, in EW-fed OVA23-3 and R23-3 mice, expression of Foxp3 on CD4+ T cells corresponded with recovery from inflammation, but recurrence of weight loss was observed on restarting the EW diet after receiving the control-diet for 1 month. No recurrence developed in D10 mice. CONCLUSIONS: Excessive IL-4 levels in the MLNs directly inhibited the induction of aiTregs and caused enteropathy. The aiTregs generated in the attenuation of T cell-dependent food allergic enteropathy may function differently than aiTregs induced in a tolerance model. Comparing the two models enables to investigate their aiTreg functions and to clarify differences between inflammation with subsequent desensitization versus tolerance.

Two distinct epitopes on the ovalbumin 323-339 peptide differentiating CD4⁺T cells into the Th2 or Th1 phenotype.

The epitopes for OVA323-339-specific CD4⁺T cells from OVA23-3 food allergy model and DO11.10 tolerant induction model mice were analyzed. We found that OVA23-3 CD4⁺T cells recognized the N-terminal region, showing strong proliferation and the Th2-phenotype, and that DO11.10 CD4⁺T cells recognized the C-terminal region, showing milder proliferation and a Th1-skewed response. These differences may regulate the responses of those mice to OVA-feeding, inflammation and tolerance.

Identification and characterization of IgG4-associated autoimmune hepatitis.

BACKGROUND: Autoimmune hepatitis (AIH) and autoimmune pancreatitis (AIP) share clinical and pathological features such as high serum levels of immunoglobulin (Ig) G and autoantibodies, and lymphoplasmacytic infiltration, suggesting the presence of common immunological abnormalities. However, little is known about the possible involvement of IgG4, a hallmark of AIP, in AIH. AIMS: In this study, we examined whether the IgG4 response contributes to the histopathological and clinical findings in AIH. METHODS: Liver sections from 26 patients with AIH, 10 patients with primary biliary cirrhosis (PBC), three patients with primary sclerosing cholangitis (PSC) and 20 chronic hepatitis patients with hepatitis C virus (HCV) infection were immunostained for IgG4. We investigated the relationship among the histopathology, the responses to steroid therapy and the IgG4 staining. RESULTS: Nine of the 26 liver specimens from patients with AIH showed positive staining for IgG4 whereas none of the 10 samples from patients with PBC, the three samples from patients with PSC or the 20 samples from patients with HCV hepatitis were positive. Patients with IgG4-positive AIH also showed increased serum levels of IgG. The numbers of T cells, B cells and plasma cells were significantly increased in the livers of patients with IgG4-positive AIH as compared with those patients with IgG4-negative AIH. Patients with IgG4-positive AIH also showed a marked response to prednisolone therapy. CONCLUSIONS: AIH may be classified into either an IgG4-associated type or an IgG4 non-associated type with the former showing a marked response to prednisolone treatment.

Isoflavones regulate innate immunity and inhibit experimental colitis.

BACKGROUND AND AIM: Dysregulated immune responses in the gut to luminal antigens can cause inflammatory bowel diseases (IBD). The roles played by dietary antigens in the pathogenesis or prevention of IBD are poorly understood. Soybean isoflavones are digested in large amounts and have many biological activities. The aim of this study was to determine whether isoflavones in aglycon and bioavailable forms have any effect on gut immunity and protect the host from tissue damage in a mouse model of colitis. METHODS: We administered daidzein-rich isoflavone aglycones (DRIA) to mice for 1 week and then treated them with 2% dextran sodium sulfate (DSS) in drinking water for 4 days to induce colitis. The effect of DRIA was evaluated by examining the histopathology of the colon, body weight changes, and functional analysis of mesenteric lymph node cells (MLN). RESULTS: DRIA inhibited interleukin (IL)-6 and IL-8 production by Toll-like receptor (TLR)2, and TLR4-stimulated monocytes in a dose-dependent manner. The mice administered DRIA had less inflammation and tissue damage in the colon than the control mice. This protective effect of DRIA was associated with a decrease in interferon-gamma, IL-6, and IL-12p40 secretion, and an increase in IL-10 secretion and low cell-activation status of antigen-presenting cells (APC) in MLN. CONCLUSION: Ingested DRIA can downregulate the functions of APC and inhibit DSS colitis.

Molecular mechanisms of portal vein tolerance.

The liver has been considered as a tolerogenic organ in the sense that favors the induction of peripheral tolerance. The administration of antigens (Ags) via the portal vein causes tolerance, which is termed portal vein tolerance and can explain the occurrence of tolerogenic responses in the liver. Here we discuss the fundamental mechanisms accounting for portal vein tolerance. Antigen-presenting cells (APCs) in the liver, especially dendritic cells and sinusoidal endothelial cells, have limited the ability to produce pro-inflammatory cytokines upon stimulation with endotoxin, an effect that could be due to the continuous exposure to bacterial Ags derived from intestinal microflora. Ag presentation by liver APCs results in T cell tolerance through clonal deletion and selection of regulatory T cells. Thus, APCs with immunosuppressive functions are associated with the achievement of portal vein tolerance via the induction of clonal deletion and generation of regulatory T cells.

Periportal and sinusoidal liver dendritic cells suppressing T helper type 1-mediated hepatitis.

BACKGROUND: Recently, we found that portal vein tolerance is associated with generation of Th2 cells and apoptosis of Th1 cells in the liver, which is regulated by antigen (Ag)-presenting dendritic cells (DCs) in the periportal area and sinusoids. AIM: In this study, we tested whether the periportal and sinusoidal DCs, which were loaded with an Ag in vivo, can inhibit liver injury caused by Th1 cells activated by the Ag administered systemically. METHODS: Ag-specific hepatitis model was created by adoptively transferring ovalbumin (OVA)-specific CD4(+) T cells to BALB/c mice and venous injection of OVA-containing liposomes. Liver CD11c(+) cells obtained from mice fed OVA were then transferred into these mice. RESULTS: The transfer of liver CD11c(+) cells from OVA-fed mice completely inhibited hepatic injury, which was associated with apoptosis of OVA-specific CD4(+) T cells and emergence of Th2 cells in the liver. Transfer of CD11c(+) cells and subcutaneous OVA challenge led to enhancement of OVA-specific IgE Ab as well as Th2 cytokine responses in the recipient mice. CONCLUSIONS: Periportal and sinusoidal DCs loaded with an Ag in the portal vein can induce Th2 response in the liver and prevent hepatic injury caused by Th1 cells.

Stroke-independent association between metabolic syndrome and functional dependence, depression, and low quality of life in elderly community-dwelling Brazilian people.

OBJECTIVES: Metabolic syndrome (Met.S) is a risk factor for stroke, dementia, and ischemic heart disease (IHD). It is unclear whether Met.S is an independent risk factor for functional dependence, depression, cognitive impairment, and low health-related quality of life (HRQoL) in a population free of clinical stroke. DESIGN: Cross-sectional. SETTING: Two communities in southern Brazil. PARTICIPANTS: Four hundred twenty people aged 60 and older. MEASUREMENTS: An adapted (body mass index > or =30 kg/m(2) and blood pressure > or =140/90) Adult Treatment Panel III definition was used in diagnosing Met.S. Depression (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Revised) and Mini-Mental State Examination were evaluated along with activities of daily living (ADLs) and instrumental activities of daily living (IADLs). HRQoL was measured using a visual analogue scale (0-10). All values were adjusted for age, sex, and presence of IHD. RESULTS: Forty (9.5%) subjects had a stroke and were excluded from the final analysis. Met.S was present in 37.4% of the stroke-free population. Met.S was significantly and independently associated with 2.24 times as much ADL dependence, 2.39 times as much IADL dependence, a 2.12 times higher risk of depression, a 2.27 times higher likelihood of cognitive impairment, and a 1.62 times higher chance of low self-perceived HRQoL (all P<0.05). Adjustment for its own components reduced the strength of the above associations but did not eliminate their statistical significance. If Met.S were removed from this population, dependence, depression, cognitive impairment, and low QoL would be reduced 15.0% to 21.4%. CONCLUSION: Met.S was significantly associated with functional dependence, depression, cognitive impairment, and low HRQoL, and its effects were independent of clinical stroke, IHD, and its own individual components.

Cognitive impairment and frontal-subcortical geriatric syndrome are associated with metabolic syndrome in a stroke-free population.

BACKGROUND: Metabolic syndrome (Met.S) consists of a conglomeration of obesity, hypertension, glucose intolerance, and dislipidemia. Frontal-subcortical geriatric syndrome (FSCS) is caused by ischemic disruption of the frontal-subcortical network. It is unknown if Met.S is associated with FSCS. METHODS: We evaluated 422 community-dwelling elderly (> or =60) in Brazil. FSCS was defined as the presence of at least one frontal release sign (grasping, palmomental, snout, or glabellar) plus coexistence of > or =3 the following criteria: (1) cognitive impairment, (2) late-onset depression, (3) neuromotor dysfunction, and (4) urgency incontinence. All values were adjusted to age and gender. RESULTS: Met.S was present in 39.3% of all subjects. Cases without any of the FSCS components represented 37.2% ('successful neuroaging' group). People with 1-3 of the FSCS components ('borderline pathological neuroaging' group) were majority (52.6%), whereas those with 4-5 of these components (FSCS group) were minority (10.2%). Met.S was significantly associated with FSCS (OR=5.9; CI: 1.5-23.4) and cognitive impairment (OR=2.2; CI: 1.1-4.6) among stroke-free subjects. Number of Met.S components explained 30.7% of the variance on the number of FSCS criteria (P<0.001). If Met.S were theoretically removed from this population, prevalence of FSCS would decline by 31.6% and that of cognitive impairment by 21.4%. CONCLUSIONS: Met.S was significantly associated with a 5.9 and 2.2 times higher chance of FSCS and cognitive impairment, respectively. Met.S might be a major determinant of 'successful' or 'pathological' neuroaging in western societies.

Nucleotide binding oligomerization domain 2 deficiency leads to dysregulated TLR2 signaling and induction of antigen-specific colitis.

In this study, we determined conditions leading to the development of colitis in mice with nucleotide binding oligomerization domain 2 (NOD2) deficiency, a susceptibility factor in Crohn's disease. We found that NOD2-deficient antigen-presenting cells (APCs) produced increased amounts of interleukin (IL)-12 in the presence of ovalbumin (OVA) peptide and peptidoglycan or recombinant E. coli that express OVA peptide (ECOVA). Furthermore, these APCs elicited heightened interferon-gamma (IFN-gamma) responses from cocultured OVA-specific CD4+ T cells. We then demonstrated that NOD2-deficient mice adoptively transferred OVA-specific CD4+ T cells and that administered intrarectal ECOVA developed colitis associated with the expansion of OVA-specific CD4+ T cells producing IFN-gamma. Importantly, this colitis was highly dependent on Toll-like receptor 2 (TLR2) function since it was suppressed in NOD2 and TLR2 double-deficient mice. Thus, NOD2-deficient mice become susceptible to colitis as a result of increased TLR2 responses when they have the capacity to respond to an antigen expressed by mucosal bacteria.

Neonatal Fc receptor for IgG regulates mucosal immune responses to luminal bacteria.

The neonatal Fc receptor for IgG (FcRn) plays a major role in regulating host IgG levels and transporting IgG and associated antigens across polarized epithelial barriers. Selective expression of FcRn in the epithelium is shown here to be associated with secretion of IgG into the lumen that allows for defense against an epithelium-associated pathogen (Citrobacter rodentium). This pathway of host resistance to a bacterial pathogen as mediated by FcRn involves retrieval of bacterial antigens from the lumen and initiation of adaptive immune responses in regional lymphoid structures. Epithelial-associated FcRn, through its ability to secrete and absorb IgG, may thus integrate luminal antigen encounters with systemic immune compartments and as such provide essential host defense and immunoregulatory functions at the mucosal surfaces.

Th response to Helicobacter pylori differs between patients with gastric ulcer and duodenal ulcer.

OBJECTIVE: Helicobacter pylori (H. pylori) infection induces both gastric (GU) and duodenal ulcers (DU). We examined whether host immunological response to H. pylori determines different disease outcomes. MATERIAL AND METHODS: Thirty-two GU and 28 DU patients infected with H. pylori, and 24 dyspeptic patients without infection were enrolled. The constituents of cellular infiltrates in biopsies from each patient were determined and lymphokines secreted by stimulated T cells were measured. Serum concentrations of IgG subclasses specific to H. pylori were measured. RESULTS: Low pepsinogen I and high pepsinogen II levels were observed in GU patients, while a high pepsinogen I level was found in DU patients. T cells predominate over other cell types in both GU and DU patients. GU patients had a higher number of T cells (p < 0.01) and lower plasma cells (p < 0.05) than those in DU patients. T cells from GU patients produced greater amounts of IFN-gamma and less IL-4 than those in DU patients (p < 0.01). GU patients had a higher serum level of IgG2 specific to H. pylori than that in DU patients (p < 0.01). CONCLUSIONS: Th response by gastric T cells in GU patient was more polarized to Th1 as compared with that in DU patients, suggesting that a distinct immune response to H. pylori induces different disease outcomes.

CD4+CD25+ T cells regulate colonic localization of CD4 T cells reactive to a microbial antigen.

BACKGROUND: In patients with inflammatory bowel diseases, T-cell activation driven by microflora has been implicated as a mechanism causing clonal expansion and infiltration of CD4+ T cells in colonic lamina propria (LP). We explored a regulatory mechanism preventing infiltration of CD4+ T cells specific to a microbe-associated antigen in the gut. METHODS: SCID mice were reconstituted with CD4+ T cells specific to ovalbumin (OVA) and were orally administered with Escherichia coli engineered to produce OVA. RESULTS: OVA-specific CD4+ T cells (KJ1-26+) were recruited to colonic LP in an Ag-dependent manner, which was inhibited by adoptive transfer of naturally occurring CD4+CD25+ T (Treg) cells. KJ1-26+ T cells and Treg cells are localized preferentially to the colonic follicles that contain dendritic cells. In mice given Treg cells, LP CD4+ T cells showed a decrease in proliferative and interferon gamma response and an increase in transforming growth factor beta1 response to OVA stimulation. Treg cells inhibited both antigenic activation of effector CD4+ T cells and class II/CD80/CD86 up-regulation of dendritic cells. CONCLUSION: : Treg cells suppress recruitment of CD4+ T cells specific to a microbe-associated antigen to LP, which was associated with colocalization of effector CD4+ T cells and Treg cells in colonic follicles.

Antigenic activation of Th1 cells in the gastric mucosa enhances dysregulated apoptosis and turnover of the epithelial cells.

Colonization of Helicobacter pylori in the stomach leads to chronic gastritis with massive infiltration by Th1 cells. To assess a role played by those T cells in the remodeling of gastric epithelium, we activated gastric T cells utilizing mice with CD4 T cells bearing transgenic TCR with or without deficiency in either IL-4 or IFN-gamma or IL-12. Mice developed gastritis upon injection of an antigen into gastric mucosa. While neutrophil infiltration occurred even with a control antigen, infiltration by transgenic T cells was dependent on the specific antigen. The numbers of epithelial cells undergoing apoptosis and regeneration were increased in the mice with infiltrating T cells producing IFN-gamma and the alignment of those cells in the glands was markedly dysregulated. In contrast, mice deficient in Th1 response showed no increase in cell division and apoptosis of epithelial cells. Thus, Th1 type T cells infiltrating into gastric mucosa play an independent role in controlling turnover of epithelial cells.