Lamina Propria Dendritic Cells Research Articles

Increase of intestinal bacterial sialidase activity exacerbates acute colitis in mice.

The availability of endogenous and dietary carbohydrates in the gastrointestinal tract influences the composition of the gut microbiota. Carbohydrate foraging requires the action of bacterially-encoded glycoside hydrolases, which release mono- and oligosaccharides taken up as carbon sources by multiple microbial taxa. In addition to providing nutrients to the microbiota, the cleavage of host glycans by bacterial glycoside hydrolases may alter the properties of surface glycoproteins involved in cell adhesion and activation processes in the gut lumen. To investigate the impact of bacterial glycoside hydrolase activities on the gut microbial composition and on host glycans during colon inflammation, we increased local glycoside hydrolase activity by supplementing mice with recombinant E. coli expressing specific sialidase, fucosidase and rhamnosidase enzymes during acute colitis induced by dextran sulfate sodium ingestion. Whereas increased fucosidase and rhamnosidase activity did not alter the course of colitis, increased sialidase activity exacerbated disease severity. The effect of increased sialidase activity on inflammation was not caused by changes in the microbial composition given that a similar shift in gut bacteria occurred in all groups of mice supplemented with recombinant E. coli. Increased sialidase activity in the colon of treated mice however significantly altered the distribution of sialic acid on mucosal glycans. Treatment of lamina propria dendritic cells with bacterial sialidase also strongly decreased the density of sialylated ligands to anti-inflammatory siglec lectins, indicating that the remodeling of surface sialylation caused by increased sialidase activity likely accounts for the observed exacerbation of acute colitis in mice.

Cholesterol-conjugated siRNAs silence gene expression in mucosal dendritic cells in cervicovaginal tissue in mice.

RNA interference (RNAi) provides a powerful way to investigate the role of genes in disease pathogenesis and modulate gene expression to treat disease. In 2018, the FDA approved patisiran, the first RNAi-based drug, hence paving the way for a novel class of RNAi therapeutics. Harnessing RNAi to inhibit vaginal HIV transmission requires effective gene silencing in immune cells, which remains difficult. Knockdown in accessible mucosal tissues may be easier than systemic gene silencing. Vaginally applied cholesterol-conjugated small interfering RNAs (chol-siRNAs) blocked herpes simplex virus transmission in mice without tissue damage or immunostimulation. To investigate using flow cytometry, confocal microscopy, and quantitative imaging if chol-siRNAs silence gene expression in vaginal immune cells in mice. Although chol-siRNAs and lipoplexed-siRNAs silence gene expression in dendritic cells (DCs) in vitro, most internalized siRNAs concentrate within multivesicular bodies, where they are inaccessible to the cellular RNAi machinery. When applied intravaginally in vivo, chol-siRNAs penetrate the vaginal mucosa, including the lamina propria, and are efficiently internalized by intraepithelial (IE) and lamina propria (LP) DCs, and CD11b+ CD45+ cells, but not by T cells. Chol-siRNAs induce partial gene silencing in IE and LP DCs throughout the genital mucosa in vivo but are inactive in F4/80+ CD11b+ macrophages and T cells. As mucosal DCs play an essential role for mucosal viral entry and dissemination, chol-siRNAs could be harnessed to target various host factors that are critical for viral uptake, DC migration and trans-infection of virions to T cells, hence allowing the development of a preventive vaginal HIV microbicide. Furthermore, chol-siRNAs could help elucidate the pathways of HIV transmission and understand the immunologic function of DCs in the genital tract.

Methylated (\u2212)-epigallocatechin 3-O-gallate potentiates the effect of split vaccine accompanied with upregulation of Toll-like receptor 5

Split-virus vaccine serves as a major countermeasure against influenza virus, but its effectiveness and protective action are not complete. We previously demonstrated the effect of Benifuuki, a green tea cultivar in Japan, on enhancing the split-virus vaccine–elicited immune response. However, little is known about the detail mechanisms. Here, we show that EGCG3”Me intake significantly potentiated the vaccine-elicited hemagglutination inhibition titer increase. Flow cytometry analysis revealed the increased Toll-like receptor 5 (TLR5) expression after EGCG3”Me treatment in lamina propria dendritic cells (LPDCs) and macrophages, which play crucial roles in the humoral immune system. TLR5 expression correlated with the level of interleukin-6 (IL-6)/C–C chemokine type receptor 5, which are important mediators of the humoral immunity. Taken together, In vivo and ex vivo studies showed that EGCG3”Me potentiated the split-virus vaccine–elicited immune response accompanied with the upregulation of TLR5 in intestine and splenocyte macrophages.

Role of TLR5 in the Translocation and Dissemination of Commensal Bacteria in the Intestine after Traumatic Hemorrhagic Shock.

Enterogenous infection is a major cause of death during traumatic hemorrhagic shock (THS). It has been reported that Toll-like receptor 5 (TLR5) plays an integral role in regulating mucosal immunity and intestinal homeostasis of the microbiota. However, the roles played by TLR5 on intestinal barrier maintenance and commensal bacterial translocation post-THS are poorly understood. In this research, we established THS models in wild-type (WT) and Tlr5−/− (genetically deficient in TLR5 expression) mice. We found that THS promoted bacterial translocation, while TLR5 deficiency played a protective role in preventing commensal bacteria dissemination after THS. Furthermore, intestinal microbiota analysis uncovered that TLR5 deficiency enhanced the mucosal biological barrier by decreasing RegIIIγ-mediated bactericidal activity against G+ anaerobic bacteria. We then sorted small intestinal TLR5+ lamina propria dendritic cells (LPDCs) and analyzed TH1 differentiation in the intestinal lamina propria and a coculture system consisting of LPDCs and naïve T cells. Although TLR5 deficiency attenuated the regulation of TH1 polarization by LPDCs, it conferred stability to the cells during THS. Moreover, retinoic acid (RA) released from TLR5+ LPDCs could play a key role in modulating TH1 polarization. We also found that gavage administration of RA alleviated bacterial translocation in THS-treated WT mice. In summary, we documented that TLR5 signaling plays a pivotal role in regulating RegIIIγ-induced killing of G+ anaerobic bacteria, and LPDCs mediated TH1 differentiation via RA. These processes prevent intestinal bacterial translocation and enterogenous infection after THS, suggesting that therapeutically targeting LPDCs or gut microbiota can interfere with bacterial translocation after THS.

COMMD10 is critical for Kupffer cell survival and controls Ly6Chi monocyte differentiation and inflammation in the injured liver.

Liver-resident macrophages Kupffer cells (KCs) and infiltrating Ly6Chi monocytes both contribute to liver tissue regeneration in various pathologies but also to disease progression upon disruption of orderly consecutive regeneration cascades. Little is known about molecular pathways that regulate their differentiation, maintenance, or inflammatory behavior during injury. Here, we show that copper metabolism MURR1 domain (COMMD)10-deficient KCs adopt liver-specific identity. Strikingly, COMMD10 deficiency in KCs and in other tissue-resident macrophages impedes their homeostatic survival, leading to their continuous replacement by Ly6Chi monocytes. While COMMD10 deficiency in KCs mildly worsens acetaminophen-induced liver injury (AILI), its deficiency in Ly6Chi monocytes results in exacerbated and sustained hepatic damage. Monocytes display unleashed inflammasome activation and a reduced type I interferon response and acquire "neutrophil-like" and lipid-associated macrophage differentiation fates. Collectively, COMMD10 appears indispensable for KC and other tissue-resident macrophage survival and is an important regulator of Ly6Chi monocyte fate decisions and reparative behavior in the diseased liver.

PD-L1+ and XCR1+ dendritic cells are region-specific regulators of gut homeostasis

The intestinal mucosa constitutes an environment of closely regulated immune cells. Dendritic cells (DC) interact with the gut microbiome and antigens and are important in maintaining gut homeostasis. Here, we investigate DC transcriptome, phenotype and function in five anatomical locations of the gut lamina propria (LP) which constitute different antigenic environments. We show that DC from distinct gut LP compartments induce distinct T cell differentiation and cytokine secretion. We also find that PD-L1+ DC in the duodenal LP and XCR1+ DC in the colonic LP comprise distinct tolerogenic DC subsets that are crucial for gut homeostasis. Mice lacking PD-L1+ and XCR1+ DC have a proinflammatory gut milieu associated with an increase in Th1/Th17 cells and a decrease in Treg cells and have exacerbated disease in the models of 5-FU-induced mucositis and DSS-induced colitis. Our findings identify PD-L1+ and XCR1+ DC as region-specific physiologic regulators of intestinal homeostasis.

Oxytocin signalling in dendritic cells regulates immune tolerance in the intestine and alleviates DSS-induced colitis.

Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD) that is associated with immune dysfunction. Recent studies have indicated that the neurosecretory hormone oxytocin (OXT) has been proven to alleviate experimental colitis. We investigated the role of OXT/OXT receptor (OXTR) signalling in dendritic cells (DCs) using mice with specific OXTR deletion in CD11c+ cells (OXTRflox/flox×CD11c-cre mice) and a dextran sulfate sodium (DSS)-induced colitis model. The level of OXT was abnormal in the serum or colon tissue of DSS-induced colitis mice or the plasma of UC patients. Both bone marrow-derived DCs (BMDCs) and lamina propria DCs (LPDCs) express OXTR. Knocking out OXTR in DCs exacerbated DSS-induced acute and chronic colitis in mice. In contrast, the injection of OXT-pretreated DCs significantly ameliorated colitis. Mechanistically, OXT prevented DC maturation through the phosphatidylinositol 4,5-bisphosphate 3-kinase (Pi3K)/AKT pathway and promoted phagocytosis, adhesion and cytokine modulation in DCs. Furthermore, OXT pre-treated DCs prevent CD4+ T cells differentiation to T helper 1 (Th1) and Th17. Our results suggest that OXT-induced tolerogenic DCs efficiently protect against experimental colitis via Pi3K/AKT pathway. Our work provides evidence that the nervous system participates in the immune regulation of colitis by modulating DCs. Our findings suggest that generating ex vivo DCs pretreated with OXT opens new therapeutic perspectives for the treatment of UC in humans.

Aberrant TNF Signaling Links RIPK3-Dependent Cell Death and Loss of TLR5 with Intestinal Inflammation and Dysbiosis

Intestinal homeostasis depends on the symbiotic nature of host-microbiota interactions. Whereas elevated TNF and dysbiosis are known hallmarks of inflammatory bowel disease (IBD), the mechanistic link between TNF, its cognate receptors, and the microbiome remains only partially understood. Using XIAP-deficiency as a murine model for a mendelian form of IBD, we show that the host-encoded TNF response cooperated with environmental cues to induce dysbiosis. Specifically, aberrant TNF signaling resulted in Paneth cell dysfunction, deregulated inflammatory pathways, and dysbiosis, which was characterized by loss of beneficial commensals. Mucosal inflammation was dependent on the individual action of TNF receptor (TNFR)1 and TNFR2. Mechanistically, aberrant TNFR2 signaling individually targeted IRF8+ lamina-propria dendritic cells to undergo MLKL-independent but RIPK3-driven cell death, whereas aberrant TNFR1 signaling also compromised Paneth cell function. Genetic loss of either receptor was sufficient to restore Clostridia and prevent intestinal inflammation. Primary patient data support the murine genetic evidence that TNFR2 promotes IBD in human patients. Our data show that the impairment of Paneth cells together with the inflammatory demise of dendritic cells is central for driving IBD and dysbiosis.

FGL2 regulates IKK/NF-κB signaling in intestinal epithelial cells and lamina propria dendritic cells to attenuate dextran sulfate sodium-induced colitis

Inflammatory bowel disease (IBD) is an autoimmune disease characterized by an abnormal immune response. Fibrinogen-like protein 2 (FGL2) is known to have immunoregulatory and anti-inflammatory activity. The level of FGL2 is elevated in patients with IBD; however, its comprehensive function in IBD is almost unknown. In our study, we explored the effect of FGL2 on dextran sulfate sodium (DSS)-induced colitis in mice and on NF-κB signaling in intestinal epithelial cells (IECs) and lamina propria dendritic cells (LPDCs). We founded that FGL2−/− mice in the colitis model showed more severe colitis manifestations than WT mice did, including weight loss, disease activity index (DAI), and colon histological scores. FGL2−/− mice treated with DSS produced more proinflammatory cytokines (IL-1β, IL-6, TNF-α) in serum than WT mice did and demonstrated upregulated expression of TNF-α and inflammatory marker enzymes, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (Cox-2) in the colon tissue. Our data suggested that DSS-treated FGL2−/− mice showed stronger activation of NF-κB signaling, especially in IECs. Next, we demonstrated that recombinant FGL2 (rFGL2) inhibited the production of proinflammatory cytokines and the expression of inflammatory marker enzymes by downregulating the NF-κB signaling in HT-29 cells. Finally, we discovered that LPDCs from the colon of DSS-treated FGL2−/− mice showed significantly upregulated expression of surface maturation co-stimulatory molecules, including CD80, CD86, CD40, and MHC class II molecules compared with that in WT mice. In addition, LPDCs in FGL2−/− treated with DSS exhibited excessive NF-κB activity and the administration of rFGL2 to FGL2−/− mice could rescue the aggravated results of FGL2−/− mice. Taken together, our findings demonstrated that FGL2 might be a target for further therapy of IBD.

Clostridium butyricum alleviates intestinal low-grade inflammation in TNBS-induced irritable bowel syndrome in mice by regulating functional status of lamina propria dendritic cells.

BACKGROUNDIrritable bowel syndrome (IBS) is one of the most common functional gas-troenterological diseases characterized by abnormal visceral sensitivity and low-grade inflammation. The role of Clostridium butyricum (C. butyricum) in reducing intestinal low-grade inflammation via immune pathways has been well defined. However, the detailed mechanisms of the effects of C. butyricum on intestinal mucosal immunity, especially on immune cells of the lamina propria, remain unclear. Dendritic cells (DCs), which are important immune cells, secrete proinflammatory cytokines (IL-1β, IL-6, and others) and express T cell immuno-globulin and mucin domain-3 (TIM3), promoting proliferation and activation of DCs, and mediating Th1 and Th17 inflammatory responses.AIMTo investigate the role of DCs in the development of IBS in a rat model and to understand the regulation of DCs after C. butyricum intervention.METHODSAn IBS animal model was established using C57BL/6 mice, and C. butyricum was continuously administered via the intragastric route to simulate different intestinal immune states. Intestinal visceral hypersensitivity and histopathology were assessed using the abdominal withdrawal reflex (AWR) test and hematoxylin & eosin (H&E) staining, respectively. The expression of proinflammatory cytokines (IL-1β and IL-6) and TIM3 was analyzed by Western blot analysis and real-time PCR. Flow cytometry was applied to analyze the quantity, function, and membrane molecule TIM3 of the lamina propria dendritic cells (LPDCs). The regulatory effect of C. butyricum was verified in bone marrow-derived dendritic cells by in vitro experiments.RESULTSThe secretion of proinflammatory cytokines (IL-1β and IL-6) in mice with IBS was significantly increased compared with that of the control group, which suggested that the intestinal mucosa in mice with IBS was in a low-grade inflammatory state. The expression of CD11C+CD80+ and CD11c+TIM3+ in intestinal LPDCs in mice with IBS increased significantly. Meanwhile, the cytokines (IL-1β and IL-6) were significantly reduced after the intervention with probiotic C. butyricum. The amount and function of LPDCs and the TIM3 on the surface of the LPDCs were decreased with the alleviation of the intestinal inflammatory response.CONCLUSIONThe results suggest that C. butyricum regulates the amount and functional status of LPDCs in the intestinal mucosa of mice with IBS, and therefore modulates the local immune response in the intestine.

BRAF V600E and Pten deletion in mice produces a histiocytic disorder with features of Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is characterized by the accumulation of Langerin (CD207)-expressing histiocytes. Mutational activation of mitogen-activated protein kinase pathway genes, in particular BRAF, drives most cases. To test whether activated BRAF is sufficient for the development of LCH, we engineered mice to express BRAF V600E under the control of the human Langerin promoter. These mice have shortened survivals, smaller lymphoid organs, absent Leydig cells, and fewer epidermal LCs than controls, but do not accumulate histiocytes. To test whether the absence of histiocyte proliferation could be due to oncogene-induced senescence, we engineered homozygous Pten loss in the same cells that expressed BRAF V600E. Like mice with intact Pten, these mice have shortened survivals, smaller thymi, and absent Leydig cells. However, loss of Pten also leads to the accumulation of CD207+ histiocytes in spleen, thymus, and some lymph nodes. While many CD207+ histiocytes in the thymus are CD8-, reminiscent of LCH cells, the CD207+ histiocytes in the spleen and lymph nodes are CD8+. These mice also accumulate large numbers of CD207- cells in the lamina propria (LP) of the small intestine. Both the lymphoid and LP phenotypes are likely due to human Langerin promoter-driven BRAF V600E expression in resident CD8+ dendritic cells in the former and LP dendritic cells in the latter and confirm that Pten loss is required to overcome inhibitory pathways induced by BRAF V600E expression. The complex phenotype of these mice is a consequence of the multiple murine cell types in which the human Langerin promoter is active.

Intestinal Goblet cells and Goblet Cell Associated Antigen Passages regulate the balance between Tregs and Th17

Abstract Tolerance towards dietary antigens and luminal microbes is essential to maintain homeostasis, the breakdown of which results in development of inflammatory bowel disease (IBD). T-helper 17 (Th17) and T-regulatory (Treg) cells are abundant in the intestinal mucosa, where they function to protect the host from pathogens and to restrain excessive effector T-cell responses, respectively. How the balance and switch between Treg and Th17 responses is maintained in the steady state to promote tolerance and how this balance becomes altered to favor Th17 responses in the setting of IBD is not known. We have identified that intestinal goblet cell (GC) associated antigen passages (GAPs), are a major pathway for steady-state luminal antigen transfer to lamina propria - dendritic cells (LP-DCs). In addition, GAPs are necessary for the imprinting of LP-DCs with tolerogenic properties, for the de novo induction of Tregs specific for dietary antigens, and the maintenance of pre-existing LP Tregs. Moreover, GAP inhibition results in the expansion of Th17 cells in the small intestine LP. Consistent with this, single cell profiling of intestinal lymphocytes revealed enhanced Th17 pathway gene signatures in mice lacking GCs. These observations strongly support that GCs/GAPs have a previously unappreciated role in maintaining the functional balance between Treg and Th17 cell.

Cell Migration Promotes the Functional Diversification of Gut Dendritic Cells

Dendritic cells (DCs) patrol tissues and transport antigens to lymph nodes to initiate adaptive immune responses. Within tissues, DCs constitute a complex cell population made of distinct subsets that express different markers and eventually display different functions. How cell-intrinsic programs and tissue-specific cues orchestrate DC diversification is only partially understood. By combining single-cell sequencing and intravital imaging, we here show that DC migration to the small intestine epithelium leads to the generation of an “immature-like” intraepithelial pool of cDC2s. These cells exhibit tolerogenic properties in contrast to lamina propria DCs, which are pro-inflammatory, resembling mature DCs. We further identify the actin motor myosin II and the nutrient-derived metabolite retinoic acid as the cell-intrinsic and -extrinsic cues driving the formation of this intraepithelial pool of cDC2s. Together, these results show that fine-tuning of DC migration controls their functional diversification within tissues.

Dendritic cell profiles in the inflamed colonic mucosa predict the responses to tumor necrosis factor alpha inhibitors in inflammatory bowel disease.

BackgroundDendritic cells play crucial roles in the control of inflammation and immune tolerance in the gut. We aimed to investigate the effects of tumor necrosis factor alpha (TNFa) inhibitors on intestinal dendritic cells in patients with inflammatory bowel disease and the potential role of intestinal dendritic cells in predicting the response to treatment.Patients and methodsIntestinal biopsies were obtained from 30 patients with inflammatory bowel disease before and after treatment with TNFa inhibitors. The proportions of lamina propria dendritic cell phenotypes were analysed using flow cytometry. Disease activity was endoscopically assessed at baseline and after the induction treatment.ResultsAt baseline, the proportion of conventional dendritic cells was higher in the inflamed mucosa (7.8%) compared to the uninflamed mucosa (4.5%) (p = 0.003), and the proportion of CD103+ dendritic cells was lower in the inflamed mucosa (47.1%) versus the uninflamed mucosa (57.3%) (p = 0.03). After 12 weeks of treatment, the proportion of conventional dendritic cells in the inflamed mucosa decreased from 7.8% to 4.5% (p = 0.014), whereas the proportion of CD103+ dendritic cells remained unchanged. Eighteen out of 30 (60%) patients responded to their treatment by week 12. Responders had a significantly higher proportion of conventional dendritic cells (9.16% vs 4.4%, p < 0.01) with higher expression of HLA-DR (median fluorescent intensity [MFI] 12152 vs 8837, p = 0.038) in the inflamed mucosa before treatment compared to nonresponders.ConclusionsA proportion of conventional dendritic cells above 7% in the inflamed inflammatory bowel disease mucosa before treatment predicts an endoscopic response to TNFa inhibitors.

Regulation of intestinal bacterial translocation by intestinal lamina propria dendritic cells expressing TLR5 after trauma/hemorrhagic shock

Regulation of intestinal bacterial translocation by intestinal lamina propria dendritic cells expressing TLR5 after trauma/hemorrhagic shock

Abrogation of TGF‐beta Signaling in Dendritic Cells Leads to E‐cadherin‐mediated Adhesion between Dendritic Cells and Epithelium which Contributes to the Pathogenesis of Inflammatory Bowel Disease

BACKGROUNDWe previously reported that a murine colitis model with dendritic cell (DC)‐ specific TGF‐beta signal deletion (CD11c‐Cre Tgfbr2fl/fl) showed Notch ligand overexpression on DCs and intestinal inflammation with goblet cell depletion. However, it has not been proved whether DC's Notch ligands are responsible for these phenotypes. Here, we establish a 3D co‐culture system of intestinal organoids with DCs to investigate the interactions between DCs and epithelium on the pathogenesis of inflammatory bowel disease (IBD), and examine therapeutic targets using this system.METHODSIn vivo, we used CD11c‐Cre Tgfbr2fl/fl mice, CD11c‐Cre Tgfbr2fl/fl Cdh1fl/fl mice and Cre‐negative mice as control. Intestinal lamina propria DCs (LPDCs) were isolated from CD11c‐Cre Tgfbr2fl/fl and control mice, and RNA extracted from these LPDCs was used for PCR array analysis of gene expressions related to adhesion molecules. We co‐cultured bone‐marrow‐ derived DCs (BMDCs) and intestinal organoids from CD11c‐Cre Tgfbr2fl/fl mice in Matrigel. A Notch inhibitor (DAPT), a Wnt inhibitor (C59), and neutralizing antibodies for Jagged1, CD103 and E‐cadherin were used for treatment.RESULTSq‐PCR array revealed LPDCs from colitic CD11c‐Cre Tgfbr2fl/fl mice had elevated expressions of many adhesion molecules, such as E‐cadherin, Integrin families, as well as Notch ligands. Oranoids co‐cultured with BMDCs from CD11c‐Cre Tgfbr2fl/fl mice changed their 3D budding structures into large cystic spheroids, but transwell‐separated BMDCs did not. Live cell imaging of organoid co‐culture system showed direct attachment of BMDCs on organoids. DAPT treatment in co‐culture retained budding structures, while C59 treatment did not. Then we evaluated the effect of neutralization of several DC surface molecules. Anti‐Jagged1 antibody or anti‐CD103 antibody did not prevent abnormal differentiation of BMDC‐co‐cultured organoids In contrast, anti‐E‐cadherin antibody significantly inhibited abnormal cyst formation. We also utilized BMDCs derived from CD11c‐Cre Tgfbr2fl/fl Cdh1fl/fl mice, which failed to induce cystic changes of organoids. In vivo, CD11c‐Cre Tgfbr2fl/fl Cdh1fl/fl mice showed attenuated colitis with sufficient goblet cells compared to CD11c‐Cre Tgfbr2fl/fl mice. Finally, we evaluated the therapeutic effect of anti‐E‐cadherin antibody on CD11c‐Cre Tgfbr2fl/fl mice, and found anti‐E‐cadherin treatment improved colitis of these mice.CONCLUSIONSAbrogation of TGF‐beta signaling in DCs upregulates E‐cadherin expression on DCs. Our data using 3D co‐culture system and IBD mouse model suggest blocking of E‐cadherin‐ mediated DCs and epithelial interactions may have therapeutic potential for IBD.Support or Funding InformationThis work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers 23590933 and 17K15717, and Asahi Life Foundation.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Goblet cell associated antigen passages are inhibited during Salmonella typhimurium infection to prevent pathogen dissemination and limit responses to dietary antigens.

Dietary antigen acquisition by lamina propria (LP) dendritic cells (DCs) is crucial to induce oral tolerance and maintain homeostasis. However, encountering innocuous antigens during infection can lead to inflammatory responses, suggesting processes may limit steady-state luminal antigen capture during infection. We observed that goblet cell (GC) associated antigen passages (GAPs), a steady-state pathway delivering luminal antigens to LP-DCs, are inhibited during Salmonella infection. GAP inhibition was mediated by IL-1β. Infection abrogated luminal antigen delivery and antigen specific T cell proliferation in the mesenteric lymph node (MLN). Antigen specific T cell proliferation to dietary antigen was restored by overriding GAP suppression; however, this did not restore regulatory T cell induction but induced inflammatory T cell responses. Salmonella translocation to the MLN required GCs and correlated with GAPs. Genetic manipulations overriding GAP suppression, or antibiotics inducing colonic GAPs, but not antibiotics that don’t, increased dissemination and worsened outcomes independent of luminal pathogen burden. Thus, steady-state sampling pathways are suppressed during infection to prevent responses to dietary antigens, limit pathogen entry, and lessen disease. Moreover, antibiotics may worsen Salmonella infection by means beyond blunting gut microbiota colonization resistance, providing new insight into how precedent antibiotic use aggravates enteric infection.

Migratory capacity and function of dendritic cells from mesenteric afferent lymph nodes after feeding a single dose of vitamin A

Lamina propria dendritic cells (DCs) have a permanent turnover with constitutive migration to mesenteric lymph nodes and replenishment by progenitors. Luminal bacteria and dietary constituents provide key signals that endow DCs their unique properties in vivo. Taking into account that the intestinal immune system is greatly influenced by retinoids, we evaluated in B6 mice 3, 8, 16 and 24 h after feeding a single dose of vitamin A phenotype and function of cells present in mesenteric afferent lymph nodes as well as signals involved in migration. We studied the frequency of CD11c+MHC-II+CD103+CD86+ and RALDH+ DCs by flow cytometry, we determined CCL-21 and D6 levels in tissue homogenates by Western blot, and we co-cultured cells isolated from afferent lymphatics with sorted CD4+ lymphocytes to assess Foxp-3 induction and homing receptor expression. Sixteen hours after vitamin A administration, DCs isolated from afferent lymphatics were able to induce homing receptors and Foxp3 expression in CD4+ lymphocytes. Our results show that a single dose of vitamin A generated a stream of signals and amplified the tolerogenic activity of DCs migrating to lymphoid tissue.

CD40-signalling abrogates induction of ROR\u03b3t+ Treg cells by intestinal CD103+ DCs and causes fatal colitis

Immune homeostasis in intestinal tissues depends on the generation of regulatory T (Treg) cells. CD103+ dendritic cells (DCs) acquire microbiota-derived material from the gut lumen for transport to draining lymph nodes and generation of receptor-related orphan γt+ (RORγt+) Helios−-induced Treg (iTreg) cells. Here we show CD40-signalling as a microbe-independent signal that can induce migration of CD103+ DCs from the lamina propria (LP) to the mesenteric lymph nodes. Transgenic mice with constitutive CD11c-specific CD40-signalling have reduced numbers of CD103+ DCs in LP and a low frequency of RORγt+Helios− iTreg cells, exacerbated inflammatory Th1/Th17 responses, high titres of microbiota-specific immunoglobulins, dysbiosis and fatal colitis, but no pathology is detected in other tissues. Our data demonstrate a CD40-dependent mechanism capable of abrogating iTreg cell induction by DCs, and suggest that the CD40L/CD40-signalling axis might be able to intervene in the generation of new iTreg cells in order to counter-regulate immune suppression to enhance immunity.

Restoring Retinoic Acid Attenuates Intestinal Inflammation and Tumorigenesis in APCMin/+ Mice.

Chronic intestinal inflammation accompanies familial adenomatous polyposis (FAP) and is a major risk factor for colorectal cancer in patients with this disease, but the cause of such inflammation is unknown. Because retinoic acid (RA) plays a critical role in maintaining immune homeostasis in the intestine, we hypothesized that altered RA metabolism contributes to inflammation and tumorigenesis in FAP. To assess this hypothesis, we analyzed RA metabolism in the intestines of patients with FAP as well as APCMin/+ mice, a model that recapitulates FAP in most respects. We also investigated the impact of intestinal RA repletion and depletion on tumorigenesis and inflammation in APCMin/+ mice. Tumors from both FAP patients and APCMin/+ mice displayed striking alterations in RA metabolism that resulted in reduced intestinal RA. APCMin/+ mice placed on a vitamin A-deficient diet exhibited further reductions in intestinal RA with concomitant increases in inflammation and tumor burden. Conversely, restoration of RA by pharmacologic blockade of the RA-catabolizing enzyme CYP26A1 attenuated inflammation and diminished tumor burden. To investigate the effect of RA deficiency on the gut immune system, we studied lamina propria dendritic cells (LPDC) because these cells play a central role in promoting tolerance. APCMin/+ LPDCs preferentially induced Th17 cells, but reverted to inducing Tregs following restoration of intestinal RA in vivo or direct treatment of LPDCs with RA in vitro These findings demonstrate the importance of intestinal RA deficiency in tumorigenesis and suggest that pharmacologic repletion of RA could reduce tumorigenesis in FAP patients. Cancer Immunol Res; 4(11); 917-26. ©2016 AACR.