Mesenteric Lymph Node Dendritic Cells Research Articles

Dominant immune tolerance in the intestinal tract imposed by RelB-dependent migratory dendritic cells regulates protective type 2 immunity

Dendritic cells (DCs) are crucial for initiating protective immune responses and have also been implicated in the generation and regulation of Foxp3+ regulatory T cells (Treg cells). Here, we show that in the lamina propria of the small intestine, the alternative NF-κB family member RelB is necessary for the differentiation of cryptopatch and isolated lymphoid follicle-associated DCs (CIA-DCs). Moreover, single-cell RNA sequencing reveals a RelB-dependent signature in migratory DCs in mesenteric lymph nodes favoring DC-Treg cell interaction including elevated expression and release of the chemokine CCL22 from RelB-deficient conventional DCs (cDCs). In line with the key role of CCL22 to facilitate DC-Treg cell interaction, RelB-deficient DCs have a selective advantage to interact with Treg cells in an antigen-specific manner. In addition, DC-specific RelB knockout animals show increased total Foxp3+ Treg cell numbers irrespective of inflammatory status. Consequently, DC-specific RelB knockout animals fail to mount protective Th2-dominated immune responses in the intestine after infection with Heligmosomoides polygyrus bakeri. Thus, RelB expression in cDCs acts as a rheostat to establish a tolerogenic set point that is maintained even during strong type 2 immune conditions and thereby is a key regulator of intestinal homeostasis.

Lactococcus lactis subsp. cremoris YRC3780 modifies function of mesenteric lymph node dendritic cells to modulate the balance of T cell differentiation inducing regulatory T cells.

The intestinal immune system plays a pivotal role in the induction of immune responses against food. In the case of T cell response, dendritic cells (DCs) are especially important. However, the regulation of immune responses to food by intestinal DCs has been poorly described. In this study, we analyzed the effect of Lactococcus lactis subsp. cremoris YRC3780, a lactic acid bacterial strain isolated from kefir, a traditional fermented milk product, on the immune responses induced by antigen presentation by intestinal DCs to T cells as well as the mechanism of action of these immunomodulatory effects. It has been shown that L. cremoris YRC3780 ameliorates the symptoms of pollinosis in both animal and human studies. CD11c+ cells from mesenteric lymph nodes (MLNs) of BALB/c mice were cultured as MLN DCs with L. cremoris YRC3780 and expression of genes inducing regulatory T cells (Tregs) was examined by qPCR. In addition, MLN DCs were cocultured with CD4+ T cells from DO11.10 transgenic mice expressing an ovalbumin (OVA)-specific TCR and the OVA antigen peptide and L. cremoris YRC3780. Induction of Tregs was examined by flow cytometry, gene expression was analyzed by DNA microarray and qPCR, and the production of cytokines was measured by ELISA. MLN DCs from TLR2-deficient mice and components of L. cremoris YRC3780 were used to examine the recognition of YRC3780 by MLN DCs. L. cremoris YRC3780 enhanced the expression of genes involved in Treg induction in MLN DCs and induced Foxp3+CD4+T cells in an MLN DC and CD4+ T-cell co-culture system. The effect on MLN DCs was likely mediated by receptors other than TLR2. Together with microarray analyses of CD4+ T cell gene expression and cytokine ELISA, it was demonstrated that L. cremoris YRC3780 promoted the induction of Th1 and Tregs, and regulated the balance of Th1/Th2 and Treg/Th17 cells involving multiple genes via the antigen-presentation of MLN DCs. Our findings provide insights into the modulation of intestinal immune responses mediated by DCs and the antiallergic effects of lactic acid bacteria.

Escherichia coli adhesion protein FimH exacerbates colitis via CD11b+CD103- dendritic cell activation.

Immune stimulators are used to improve vaccine efficiency; however, they are accompanied by various side effects. In previous studies, we reported that the Escherichia coli adhesion protein, FimH, induces immune activity; however, we did not examine any side effects in colon inflammation. FimH was administered orally or intraperitoneally (i.p.) to mice with dextran sulfate sodium (DSS)-induced colitis, and changes in symptoms were observed. Immune cells infiltrated into the colon after the induction of colon inflammation were analyzed using a flow cytometer. Changes in Th1 and Th17 cells that induce colitis were analyzed. Further, mesenteric lymph node (mLN) dendritic cells (DCs) activated by FimH were identified and isolated to examine their ability to induce T-cell immunity. FimH oral and i.p. administration in C57BL/6 mice did not induce inflammation in the colon; however, DSS-induced colitis was exacerbated by oral and i.p. FimH administration. FimH treatment increased immune cell infiltration in the colon compared to that in DSS colitis. Th1 and Th17 cells, which are directly related to colitis, were increased in the colon by FimH; however, FimH did not directly affect the differentiation of these T cells. FimH upregulated the CD11b+CD103- DC activity in the mLNs, which produced the signature cytokines required for Th1 and Th17. In addition, isolated CD11b+CD103- DCs, after stimulation with FimH, directly induced Th1 and Th17 differentiation in a co-culture of CD4 T cells. This study demonstrated the side effects of FimH and indicated that the use of FimH can aggravate the disease in patients with colitis.

Opposing Roles of DCs and iNKT Cells in the Induction of Foxp3 Expression by MLN CD25+CD4+ T Cells during IFNγ-Driven Colitis

We have previously shown that a deficiency of CD1d-restricted invariant natural killer T (iNKT) cells exacerbates dextran sulfate sodium (DSS)-induced colitis in Yeti mice that exhibit IFNγ-mediated hyper-inflammation. Although iNKT cell-deficiency resulted in reduced Foxp3 expression by mesenteric lymph node (MLN) CD4+ T cells in DSS-treated Yeti mice, the cellular mechanisms that regulate Foxp3 expression by CD25+CD4+ T cells during intestinal inflammation remain unclear. We found that Foxp3-CD25+CD4+ T cells expressing Th1 and Th17 phenotypic hallmarks preferentially expanded in the MLNs of DSS-treated Yeti/CD1d knockout (KO) mice. Moreover, adoptive transfer of Yeti iNKT cells into iNKT cell-deficient Jα18 KO mice effectively suppressed the expansion of MLN Foxp3-CD25+CD4+ T cells during DSS-induced colitis. Interestingly, MLN dendritic cells (DCs) purified from DSS-treated Yeti/CD1d KO mice promoted the differentiation of naive CD4+ T cells into Foxp3-CD25+CD4+ T cells rather than regulatory T (Treg) cells, indicating that MLN DCs might mediate Foxp3+CD25+CD4+ T cell expansion in iNKT cell-sufficient Yeti mice. Furthermore, we showed that Foxp3-CD25+CD4+ T cells were pathogenic in DSS-treated Yeti/CD1d KO mice. Our result suggests that pro-inflammatory DCs and CD1d-restricted iNKT cells play opposing roles in Foxp3 expression by MLN CD25+CD4+ T cells during IFNγ-mediated intestinal inflammation, with potential therapeutic implications.

Effect of polyvinyl butyrate nanoparticles incorporated with immune suppressing vitamins on alteration of population of intestinal immune cells

The nanoparticles (NPs) from polyvinyl butyrate (PVBu) which can work as an orally applicable donor of butyrate for intestine were prepared. Immunotolerance inducing molecules such as vitamin D3 and all-trans retinoic acid (ATRA) were incorporated into PVBu NPs. The alteration in populations and numbers of DC103+ dendritic cells (DC) and regulatory T (Treg) cells in intestinal immune tissues were examined after oral administration of NPs. It was found that NPs reduced the population of CD103+ DC and Treg cells in Peyer’s patched in lower part of the intestine and inversely increased the population of CD103+ DC in mesenteric lymph node (MLN), while the population of Treg cells in MLN was unchanged. These observations indicate that NPs may enhance the immunotolerance at MLN and lamina propria toward luminal antigens, indicating the promising features of PVBu NPs as therapeutics of allergy and autoimmune diseases.

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.

Myeloid Cell Expression of LACC1 Is Required for Bacterial Clearance and Control of Intestinal Inflammation

Loss-of-function variants in the laccase domain containing 1 (LACC1) gene are associated with immune-mediated diseases, including inflammatory bowel disease. It is not clear how LACC1 balances defenses against intestinal bacteria vs intestinal inflammation or what cells are responsible for this balance in humans or mice. Lacc1-/- mice and mice with myeloid-specific disruption of Lacc1 (Lacc1Δmye) were given oral Salmonella Typhimurium or dextran sodium sulfate. CD45RBhiCD4+T cells were transferred to Lacc1-/-Rag2-/- mice to induce colitis. Organs were collected and analyzed by histology and protein expression. Bone marrow-derived macrophages and dendritic cells, lamina propria macrophages, and mesenteric lymph node dendritic cells were examined. We performed assays to measure intestinal permeability, cell subsets, bacterial uptake and clearance, reactive oxygen species, nitrite production, autophagy, signaling, messenger RNA, and cytokine levels. Lacc1-/- mice developed more severe T-cell transfer colitis than wild-type mice and had an increased burden of bacteria in intestinal lymphoid organs, which expressed lower levels of T helper (Th) 1 and Th17 cytokines and higher levels of Th2 cytokines. Intestinal lymphoid organs from mice with deletion of LACC1 had an increased burden of bacteria after oral administration of S Typhimurium and after administration of dextran sodium sulfate compared with wild-type mice. In macrophages, expression of LACC1 was required for toll-like receptor-induced uptake of bacteria, which required PDK1, and of mitogen-activated protein kinase (MAPK)- and nuclear factor κB-dependent induction of reactive oxygen species, reactive nitrogen species, and autophagy. Expression of LACC1 by dendritic cells was required for increasing expression of Th1 and Th17 cytokines and reducing expression of Th2 cytokines upon coculture with CD4+ T cells. Mice with LACC1-deficient myeloid cells had an increased burden of bacteria and altered T-cell cytokines in intestinal lymphoid organs, similar to Lacc1-/- mice. Complementation of cytokines produced by myeloid cells to cocultures of LACC1-deficient myeloid cells and wild-type CD4+ T cells restored T-cell cytokine regulation. When S Typhimurium-infected Lacc1Δmye mice were injected with these myeloid cell-derived cytokines, intestinal tissues increased production of Th1 and Th17 cytokines, and bacteria were reduced. Disruption of Lacc1 in mice increases the burden of bacteria in intestinal lymphoid organs and intestinal inflammation after induction of chronic colitis. LACC1 expression by myeloid cells in mice is required to clear bacteria and to regulate adaptive T-cell responses against microbes.

Gut dysbiosis modulates the immune response to factor VIII in murine hemophilia A

AbstractThe development of neutralizing FVIII antibodies is the most serious complication of hemophilia A treatment. The currently known patient- and treatment-related risk factors for inhibitor development do not accurately predict this adverse event in all patients. The composition of the gut microbiota has been shown to influence immune-mediated diseases at distant anatomical sites (eg, lungs, brain, and joints). We demonstrate that a disrupted gut microbiota can be created in a mouse model of hemophilia A using a broad-spectrum antibiotic. Under controlled conditions, this sustained dysbiosis was associated with an increase in splenic B cells and the development of higher titer, FVIII-specific immunoglobulin G antibodies after FVIII challenge. Splenic and mesenteric lymph node cytokines, T cells, and dendritic cells were unaffected before administration of FVIII. However, the immune transcriptome of both aforementioned secondary lymphoid organs was significantly modified. Short-chain fatty acids (SCFAs), which are immunomodulatory microbial metabolites, were depleted in cecal contents of the dysbiotic mice. Furthermore, supplementation of the drinking water with butyrate, the most immunologically active SCFA, successfully achieved attenuation of the FVIII immune response. Collectively, data from this exploratory study suggest that the composition of the gut microbiota alters the FVIII immune response via the action of specific microbial metabolites on the immune cell transcriptome and that oral supplementation with butyrate effectively reduces the FVIII immune response.

Lactobacillus plantarum OLL2712 induces IL-10 production by intestinal dendritic cells.

Recently many researchers have revealed that certain lactic acid bacteria (LAB) have beneficial effects on the immune system. Understanding the mechanisms of how certain LAB induce immunomodulatory functions is important for the development of food ingredients that improve our health. Lactobacillus plantarum OLL2712 has been shown to induce production of interleukin (IL)-10, an anti-inflammatory cytokine, by murine in vitro-induced dendritic cells (DCs) and peritoneal macrophages. However, it is probable that in vitro-induced DCs have different properties compared with intestinal DCs, and the effects of the LAB on intestinal DCs are not fully understood. In this report, we investigated whether L. plantarum OLL2712 had efficacy for inducing intestinal DCs to produce IL-10 in vitro and whether oral administration of the bacteria induced the same effect. Co-culture of L. plantarum OLL2712 with purified DCs from the mesenteric lymph node (MLN) or Peyer’s patch (PP) elevated IL-10 mRNA expression and protein production by both kinds of DCs. Addition of the LAB enhanced IL-10 production by T cells during antigen-specific responses in co-culture of MLN or PP DCs and T cells. Oral administration of L. plantarum OLL2712 for 6 days increased IL-10 gene expression in MLN DCs, and upregulated IL-10 gene expression in PP DCs was observed 12 hr after oral administration of the LAB. Our results suggested that L. plantarum OLL2712 could modulate immune responses by enhancing IL-10 production from intestinal DCs.

Isoproterenol Disrupts Intestinal Barriers Activating Gut-Liver-Axis: Effects on Intestinal Mucus and Vascular Barrier as Entry Sites

Background: The gut-liver-axis presents the pathophysiological hallmark for multiple liver diseases and has been proposed to be modulated during stress and shock. Access to the gut-liver-axis needs crossing of the mucus and gut-vascular barrier. The role of β-adrenoreceptor-activation for both barriers has not been defined and is characterized here. Methods: Splanchnic β-adrenergic stimulation was achieved by chronic intraperitoneal application of isoproterenol via alzet-pump in vivo. The intestinal permeability and gut-vascular barrier function was assessed in ileal loop experiments. The extravasation of predefined sizes of fluorescence isothiocyanate (FITC)-dextran molecules in ileal microcirculation was evaluated by intravital confocal laser endomicroscopy in vivo. Mucus parameters thickness, goblet cell count and mucin-expression were assessed by stereomicroscopy, immunostaining and RNA-sequencing respectively. Ileal lamina propria (LP) as well as mesenteric lymph node mononuclear cells was assessed by FACS. Results: Healthy mice lack translocation of 4 kDa-FITC-dextran from the small intestine to the liver, whereas isoproterenol-treated mice demonstrate pathological translocation (PBT). Mucus layer is reduced in thickness with loss of goblet-cells and mucin-2-staining and -expression in isoproterenol-treated animals under standardized gnotobiotic conditions. Isoproterenol disrupts the gut vascular barrier displaying Ileal extravasation of large-sized 70- and 150 kDa-FITC-dextran. This pathological endothelial permeability and accessibility induced by isoproterenol associates with an augmented expression of plasmalemmal-vesicle-associated-protein-1 in intestinal vessel. Ileal LP after isoproterenol treatment contains more CD11c+-dendritic cells (DC) with increased appearance of CCR7+ DC in mesenteric lymph nodes. Conclusions: Isoproterenol impairs the intestinal muco-epithelial and endothelial-vascular barrier promoting PBT to the liver. This barrier dysfunction on multiple levels potentially can contribute to liver injury induced by catecholamines during states of increased β-adrenergic drive.

Differential Roles of Dendritic Cells in Expanding CD4 T Cells in Sepsis.

Sepsis is a systemically dysregulated inflammatory syndrome, in which dendritic cells (DCs) play a critical role in coordinating aberrant immunity. The aim of this study is to shed light on the differential roles played by systemic versus mucosal DCs in regulating immune responses in sepsis. We identified a differential impact of the systemic and mucosal DCs on proliferating allogenic CD4 T cells in a mouse model of sepsis. Despite the fact that the frequency of CD4 T cells was reduced in septic mice, septic mesenteric lymph node (MLN) DCs proved superior to septic spleen (SP) DCs in expanding allogeneic CD4 T cells. Moreover, septic MLN DCs markedly augmented the surface expression of MHC class II and CD40, as well as the messaging of interleukin-1β (IL-1β). Interestingly, IL-1β-treated CD4 T cells expanded in a dose-dependent manner, suggesting that this cytokine acts as a key mediator of MLN DCs in promoting septic inflammation. Thus, mucosal and systemic DCs were found to be functionally different in the way CD4 T cells respond during sepsis. Our study provides a molecular basis for DC activity, which can be differential in nature depending on location, whereby it induces septic inflammation or immune-paralysis.

CCR7-deficient mice exhibit a delayed antigen-specific mucosal IgA antibody response to an oral recombinant Salmonella strain.

The migration of antigen (Ag)-loading dendritic cells (DCs) from Peyer's patches (PPs) to the draining mesenteric lymph nodes (MLNs) via chemokine receptor 7 (CCR7) is thought to be an important step in the initiation of acquired immunity. Our previous study showed that PPs were indispensable for Ag-specific secretory (S)IgA antibody (Ab) responses against oral recombinant Salmonella (rSalmonella). In this study, we attempted to show direct PP DC migration to MLNs by employing photoconvertible protein transgenic mice and investigated the role of the CCR7 signaling pathway in mucosal IgA induction. Our results demonstrated an actual flux of DCs from PPs to MLNs. The frequency of CCR7+ CD11c+ DCs in MLNs of PP-deficient mice was reduced, suggesting that some PP DCs migrated via CCR7. Immunization of CCR7-/- mice elicited significantly lower levels of Ag-specific SIgA Ab responses, which was associated with diminished formation of the germinal center in PPs. However, increased SIgA Ab production and dissemination of rSalmonella were observed at later time points. These results suggest that, although CCR7 was required for SIgA induction at normal velocity, the CCR7-mediated pathway is not essential for the induction of Ag-specific SIgA Ab responses to rSalmonella.

P156 PSYCHOLOGICAL STRESS INDUCES ALTERATIONS IN BEHAVIOR AND THE MUCOSAL IMMUNE SYSTEM IN A SPONTANEOUS MOUSE MODEL OF ILEITIS

Patients with Crohn’s disease (CD) suffer from abnormally high rates of depression and anxiety. Depression among patients with CD are higher than other debilitating chronic medical conditions, such as cancer. Behavioral co-morbidities are associated with increased rates of flares, more severe disease course, and increased rate of corticosteroid prescription. Psychological stress, even among CD patients in remission, is recognized as a risk factor for flare-ups. Despite the well-established relationship between stress and symptom relapse, a rigorous mechanistic explanation remains elusive. Here we demonstrate alterations in the behavioral profile and the mucosal immune system in the SAMP1/YitFc (SAMP1) mouse, a spontaneous model of CD-like ileitis, following exposure to acute and chronic psychological stress. SAMP1 littermates were sex matched and divided into two groups (n=8). The first group was subjected to restraint stress (RS) for seven days. Mice were restrained for 180 minutes per day in a 50mL conical tube with air holes drilled for adequate ventilation. Stool samples were collected each day. Subsequently, each group was subjected to behavioral testing to determine anxiety-like behavior (open field and elevated plus maze), depressive-like behavior (tail suspension), motor deficits (line crossings and rota-rod), and cognitive deficits (Y-maze). Immediately after, mice were sacrificed and tissue samples were collected for immunological analysis. Mice subjected to RS displayed increased immobility time during tail suspension indicating a depressive-like phenotype (p < 0.05). All other behavioral characteristics remained unchanged compared to control. Interestingly, FACS analysis revealed that RS mice had a marked increase in mesenteric lymph node (MLN) dendritic cells (p < 0.01) despite similar T-cell populations. Further analysis, including histopathology, serum cytokine ELISA, fecal corticosterone, 16s rRNA analysis of the microbiome, and RT-PCR analysis of ileum and spleen are currently underway and will be ready by the end of the year. The marked difference in the MLN dendritic cell (DC) population suggests increased luminal sampling of intestinal bacteria. Determining how the microbiome affects or is affected by the altered DC population is of particular interest to us. Is the DC population altered because of the microbiome or is the DC population altering the microbiome? Our preliminary data has suggested that depressive states are associated with alterations in the microbiome. Again, whether the changes are a cause or an effect of depression is yet to be answered but is our immediate goal.

Effects of Lactobacillus rhamnosus GG on the maturation and differentiation of dendritic cells in rotavirus-infected mice.

Rotavirus-related diarrhoea is considered one of the most important diseases in field animal production. In addition to the classic vaccine strategy, a number of studies have utilised probiotics, such as Lactobacillus rhamnosus GG (LGG), to prevent rotavirus-induced diarrhoea. Although it has been partially revealed that Toll-like receptors (TLRs) are involved in the LGG-mediated protection against rotavirus infection, the details of the underlying immunologic mechanisms remain largely unknown. In this study, three-to-four-week-old female BALB/c mice were divided into three groups and orally administered phosphate buffered saline (PBS), PBS plus rotavirus or LGG plus rotavirus, respectively. The differentiation and maturation of dendritic cells (DCs) were then determined by FACS, the expression levels of TLR-3 and nuclear factor kappa beta (NF-κB) were evaluated using real time PCR, and the production of inflammatory cytokines in mesenteric lymph nodes (MLNs) were determined by ELISA. The results demonstrated that rotavirus infection significantly increased the percentage of CD11c+CD11b+CD8a- DCs and decreased the percentage of CD11c+CD11b-CD8a+ DCs in MLNs. By contrast, the presence of LGG significantly decreased the percentage of CD11c+CD11b+CD8a- DCs and increased the percentage of CD11c+CD11b-CD8a+ DCs, which indicates that the differentiation of DCs is involved in the protective effects of LGG. Rotavirus infection also resulted in the increased expression of surface markers such as CD40, CD80 and MHC-II in DCs, and the administration of LGG significantly increased the expression level further. The mRNA levels of TLR-3 and NF-κB in the intestine and MLNs were also significantly increased in the presence of rotavirus, which was further increased in the presence of LGG. The production of inflammatory cytokines was also determined, and the results showed that rotavirus caused the increased production of interleukin (IL)-12 and tumour necrosis factor alpha; this effect was further enhanced by LGG. Meanwhile, although rotavirus infection led to the increased production of IL-6 and IL-10, the presence of LGG significantly decreased the mRNA levels of these cytokines. By contrast, rotavirus infection resulted in the decreased production of interferon gamma (IFN-γ), and the administration of LGG significantly increased the levels of IFN-γ. Taken together, the protective effects of LGG were partially due to the modulation of the differentiation and maturation of DCs, the increased production of TLR-3 and NF-κB, and the modulation of inflammatory cytokines.

SIgA–Shigella Immune Complexes Interact with Dectin-1 and SIGNR3 to Differentially Regulate Mouse Peyer's Patch and Mesenteric Lymph Node Dendritic Cell's Responsiveness

In addition to contributing to immune exclusion at mucosal surfaces, secretory IgA (SIgA) made of polymeric IgA and secretory component is able to selectively reenter via microfold cells into Peyer's patches (PPs) present along the intestine and to associate with dendritic cells (DCs) of the CD11c+CD11b+MHCII+F4/80−CD8−phenotype in the subepithelial dome region and the draining mesenteric lymph nodes (MLNs). However, the nature of the receptor(s) for SIgA on murine PP and MLN DCs is unknown. We find that glycosylated secretory component moiety and polymeric IgA are both involved in the specific interaction with these cells. Using blocking antibodies and competition experiments, we identify Dectin-1 and specific intercellular adhesion molecule-3 grabbing non-integrin receptor 3 (SIGNR3) as receptors for SIgA. While SIgA-commensal immune complexes (ICs) contribute to local homeostasis upon interaction with mucosal DCs, the picture is less clear for pathogenic agents. We find that in comparison with incubation of Shigella flexneri alone, association of the enteropathogen with SIgA prompts freshly isolated DCs from PPs and MLNs to invert the production of pro- versus non-inflammatory cytokines/chemokines. The sum of the data suggests that in contrast to IgG-based ICs boosting immune reactivity of antigen-presenting cells, SIgA produced during an ongoing immune response can, in addition to its known function of immune exclusion, modulate mucosal DC conditioning via specific interaction with Dectin-1 and SIGNR3.

Mesenteric lymph node CD11b- CD103+ PD-L1High dendritic cells highly induce regulatory T cells.

Dendritic cells (DCs) in mesenteric lymph nodes (MLNs) induce Foxp3+ regulatory T cells to regulate immune responses to beneficial or non-harmful agents in the intestine, such as commensal bacteria and foods. Several studies in MLN DCs have revealed that the CD103+ DC subset highly induces regulatory T cells, and another study has reported that MLN DCs from programmed death ligand 1 (PD-L1) -deficient mice could not induce regulatory T cells. Hence, the present study investigated the expression of these molecules on MLN CD11c+ cells. Four distinct subsets expressing CD103 and/or PD-L1 were identified, namely CD11b+ CD103+ PD-L1High , CD11b- CD103+ PD-L1High , CD11b- CD103+ PD-L1Low and CD11b+ CD103- PD-L1Int . Among them, the CD11b- CD103+ PD-L1High DC subset highly induced Foxp3+ T cells. This subset expressed Aldh1a2 and Itgb8 genes, which are involved in retinoic acid metabolism and transforming growth factor-β (TGF-β) activation, respectively. Exogenous TGF-β supplementation equalized the level of Foxp3+ T-cell induction by the four subsets whereas retinoic acid did not, which suggests that high ability to activate TGF-β is determinant for the high Foxp3+ T-cell induction by CD11b- CD103+ PD-L1High DC subset. Finally, this subset exhibited a migratory DC phenotype and could take up and present orally administered antigens. Collectively, the MLN CD11b- CD103+ PD-L1High DC subset probably takes up luminal antigens in the intestine, migrates to MLNs, and highly induces regulatory T cells through TGF-β activation.

Forkhead box protein 3 demethylation is associated with tolerance induction in peanut-induced intestinal allergy

Regulatory T (Treg) cells play an essential role in the maintenance of immune homeostasis in allergic diseases. We sought to define the mechanisms underlying induction of tolerance to peanut protein and prevention of the development of peanut allergy. High or low doses of peanut extract were administered to pups every day for 2weeks before peanut sensitization and challenge. After challenge, symptoms, Treg cell numbers, and forkhead box protein 3 (Foxp3), TH2 and TH17 cytokine, and Tgfβ expression in mesenteric lymph node (MLN) CD4+ T cells and jejunum were monitored. Treg cell suppressive activity and Foxp3 methylation in MLN CD4+ T cells were assayed. Feeding high but not low doses of peanut before sensitization induced tolerance, as demonstrated by prevention of diarrhea and peanut-specific IgE responses, increases in the percentage of CD4+CD25+FoxP3+ cells in MLNs, and Foxp3 mRNA and protein expression in CD4+ cells from MLNs or jejunum. Feeding high doses of peanut before sensitization decreased percentages of CD3+CD4+IL-13+ and CD3+CD4+IL-17+ cells in MLNs and decreased Il13 and Il17a and increased Tgfβ mRNA expression in the jejunum; numbers of CD103+ dendritic cells in MLNs were significantly increased. Treg cell suppression was shown to be antigen specific. Foxp3 methylation was increased in peanut extract-sensitized and challenged mice, whereas in tolerized mice levels were significantly reduced. Feeding high doses of peanut to pups induced tolerance to peanut protein. Foxp3 demethylation was associated with tolerance induction, indicating that Treg cells play an important role in the regulation of peanut sensitivity and maintenance of immune homeostasis.

Diet-Derived Short Chain Fatty Acids Stimulate Intestinal Epithelial Cells To Induce Mucosal Tolerogenic Dendritic Cells.

The gastrointestinal tract is continuously exposed to many environmental factors that influence intestinal epithelial cells and the underlying mucosal immune system. In this article, we demonstrate that dietary fiber and short chain fatty acids (SCFAs) induced the expression of the vitamin A-converting enzyme RALDH1 in intestinal epithelial cells in vivo and in vitro, respectively. Furthermore, our data showed that the expression levels of RALDH1 in small intestinal epithelial cells correlated with the activity of vitamin A-converting enzymes in mesenteric lymph node dendritic cells, along with increased numbers of intestinal regulatory T cells and a higher production of luminal IgA. Moreover, we show that the consumption of dietary fiber can alter the composition of SCFA-producing microbiota and SCFA production in the small intestines. In conclusion, our data illustrate that dietary adjustments affect small intestinal epithelial cells and can be used to modulate the mucosal immune system.

Allicin ameliorates intraintestinal bacterial translocation after trauma/hemorrhagic shock in rats: The role of mesenteric lymph node dendritic cell

Intestinal dendritic cells play important roles in regulating the function of the intestinal immune barrier and the intestinal bacterial translocation. In this study, we aim to investigate the effects of allicin on the function of mesenteric lymph node-dendritic cells after trauma/hemorrhagic shock. One hundred and eight-four Sprague-Dawley rats were randomly assigned into a sham group (n=46), sham+allicin group (n=46), trauma/hemorrhagic shock group (n=46), and trauma/hemorrhagic shock+allicin group (n=46). Studies were performed on an invivo model of spontaneously breathing rats with induced trauma/hemorrhagic shock. Allicin was diluted in resuscitation fluid and was administered through the right jugular vein. Flow cytometry was used to determine the expression of CD80, CD86, and major histocompatibility complex II (MHC II) on the surface of mesenteric lymph node-dendritic cells, as well as apoptosis. Intraintestinal bacterial translocation was monitored by using bioluminescent citrobacter. Intestinal permeability tests were conducted by using both FITC-Dextran and Ussing-Chember assay. CD80 and MHC-II expression levels were downregulated in the trauma/hemorrhagic shock group compared with the sham and sham+allicin groups; however, the expression was upregulated after allicin treatment. Also, allicin could ameliorate the trauma/hemorrhagic shock-induced increase in early apoptosis of mesenteric lymph node-dendritic cells. A significant increase was observed in the permeability of the intestinal barrier after severe traumatic shock, along with an obvious intraintestinal bacterial translocation to mesenteric lymph node. No difference was noticed in the bacterial translocation in mesenteric lymph node in the trauma/hemorrhagic shock group compared with trauma/hemorrhagic shock+allicin group (P=.589), which indicated allicin could not block bacterial translocation into mesenteric lymph node after trauma/hemorrhagic shock. However, it may increase the capacity of mesenteric lymph node to block intraintestinal bacterial translocation to extraintestinal organs as a statistical difference was noticed in the bacterial translocation in liver, blood, and spleen between trauma/hemorrhagic shock and trauma/hemorrhagic shock+allicin groups (P<.05). Trauma/hemorrhagic shock resulted in a decrease of mature mesenteric lymph node-dendritic cells. Allicin treatment could block intraintestinal bacterial translocation through increasing the immunologic barrier function of mesenteric lymph node by modulating dendritic cells maturation.

4,4'-diaponeurosporene, a C30 carotenoid, effectively activates dendritic cells via CD36 and NF-κB signaling in a ROS independent manner.

Carotenoids could be divided into C30 carotenoids and C40 carotenoids. The immune functions of C40 carotenoids had been extensively researched, while those of C30 carotenoids still remain unclear. In this study, the immune functions of a biosynthetic C30 carotenoid, 4,4′-diaponeurosporene (Dia), were identified on dendritic cells (DCs). DCs treated with 1 μM Dia for 24 h showed morphologic and phenotypic characteristics of mature state and had an increased production of IL-6, IL-10, IL-12p70 and TNFα, while β-carotene had a suppressive effect on DCs maturation. Moreover, Dia promoted antigen uptake of DCs in vitro and increased the quantity of antigen loaded DCs in mesenteric lymph nodes (MLN). Dia-treated DCs also had an enhanced ability to stimulate T cell proliferation and Th1 polarization. Further researches showed that Dia activated DCs via CD36 as well as ERK, JNK, and NF-κB signals in a reactive oxygen species (ROS) independent manner.