Disrupted regulatory T cell homeostasis in inflammatory bowel diseases

NPSR1 promotes chronic colitis through regulating CD4+ T cell effector function in inflammatory bowel disease

BACKGROUND

Neuropeptide S receptor 1 (NPSR1) has been implicated in the the onset of inflammatory bowel disease (IBD), though its exact mechanism remains unclear. This study investigates the role of NPSR1 in regulating CD4+ T cell effector function in IBD.

METHODS

Peripheral blood and colonic mucosal biopsies from IBD patients, as well as dextran sodium sulfate (DSS)-induced mouse colitis models, were analyzed to assess the effects of NPSR1 on colitis and CD4+ T cell-mediated immune responses. NPSR1 knockdown was conducted both in vitro and in vivo to elucidate underlying mechanisms. Expression of NPSR1 and CD4+ T cell-related factors was measured using quantitative real-time PCR, immunoblotting, cytometric bead array, immunofluorescence, and immunohistochemistry. CD4 + T cell effector functions were evaluated through flow cytometry, EdU incorporation assay, Annexin V-FITC/PI staining, and transwell assay.

RESULTS

NPSR1 expression was elevated in the intestinal tissues from IBD patients. Its downregulation provided protection in DSS-induced mouse colitis models. NPSR1 correlated positively with CD4 + T cell-mediated inflammation, and its knockdown reduced CD4+ T cell-mediated immune responses and inhibited CD4+ T cell differentiation. Additionally, NPSR1 knockdown decreased CD4+ T cell proliferation, increased apoptosis, and enhanced CCL2-induced migration in vitro, while significantly reducing Th1 cell chemotaxis in vivo.

CONCLUSIONS

This study demonstrates that NPSR1 promotes chronic colitis by regulating CD4 + T cell effector functions in IBD, offering potential new therapeutic strategies for IBD treatment.

PARP1 inactivation increases regulatory T / Th17 cell proportion in intestinal inflammation. Role of HMGB1

Inflammatory bowel diseases (IBD) are chronic relapsing disorders with increasing prevalence. Knowledge gaps still limit the possibility to develop more specific and effective therapies. Using a dextran sodium sulfate colitis mouse model, we found that inflammation increased the total number and altered the frequencies of leukocytes within colon mesenteric lymph nodes (cMLNs). Although the inflammation reduced the frequency of regulatory T (Treg) cells, their absolute numbers were increased. Increased frequency of colitogenic Th17 cells was also observed. Noteworthy, untreated mice lacking Poly(ADP-ribose)-Polimerase-1 functional gene (PARP-1KO) displayed higher frequency of Treg cells and lower percentage of Th17 cells in cMLNs. In colitic PARP-1KO mice the inflammation driven expansion of the Foxp3 Treg population was more pronounced than in WT mice. Conversely, colitis increased Th17 cells to a lower extent in PARP-1KO mice compared with WT mice, resulting in a more protective Treg/Th17 cell ratio. Consequently PARP-1KO mice developed less severe colitis with reduced expression of inflammatory cytokines. In ex vivo experiments PARP-1KO and WT CD11c dendritic cells (DCs) promoted naïve CD4 T cell differentiation differently, the former sustaining more efficiently the generation of Treg cells, the latter that of Th17 cells. Addition of HMGB1 B box or of dipotassium glycyrrhizate, which sequesters extracellular HMGB1, revealed a role for this alarmin in the regulation exerted by PARP-1 on the stimulating vs. tolerogenic function of DCs during colitis. Moreover, a higher percentage of CD11c DC from PARP-1KO mice expressed CD103, a marker associated with the ability of DC to induce Treg cells, compared with WT DC. Conversely, PARP-1KO DC were including a reduced percentage of CX3CR1+ DC, described to induce Th17 cells. These findings were observed in both splenic and colon lamina propria DC.

Regulatory T Cell Dysfunction in Autoimmune Diseases

Regulatory T cells (Tregs), a suppressive subpopulation of T cells, are potent mediators of peripheral tolerance, responsible for immune homeostasis. Many autoimmune diseases exhibit disruptions in Treg function or quantity, resulting in an imbalance between protective and pathogenic immune cells. Selective expansion or manipulation of Tregs is a promising therapeutic approach for autoimmune diseases. However, the extensive diversity of Treg subpopulations and the multiple approaches used for Treg identification leads to high complexity, making it difficult to develop a successful treatment capable of modulating Tregs. In this review, we describe the suppressive mechanisms, subpopulations, classification, and identification methodology for Tregs, and their role in the pathogenesis of autoimmune diseases.

Regulatory role of PI16 in autoimmune arthritis and intestinal inflammation: implications for Treg cell differentiation and function

BACKGROUND

Regulatory T cells (Tregs) are crucial in maintaining immune homeostasis and preventing autoimmunity and inflammation. A proportion of Treg cells can lose Foxp3 expression and become unstable under inflammation conditions. The precise mechanisms underlying this phenomenon remain unclear.

METHODS

The PI16 gene knockout mice (PI16fl/flFoxp3Cre) in Treg were constructed, and the genotypes were identified. The proportion and phenotypic differences of immune cells in 8-week-old mice were detected by cell counter and flow cytometry. Two groups of mouse Naïve CD4+T cells were induced to differentiate into iTreg cells to observe the effect of PI16 on the differentiation and proliferation of iTreg cells, CD4+CD25+Treg and CD4+CD25- effector T cells (Teff) were selected and co-cultured with antigen presenting cells (APC) to observe the effect of PI16 on the inhibitory ability of Treg cells in vitro. The effects of directed knockout of PI16 in Treg cells on inflammatory symptoms, histopathological changes and immune cell expression in mice with enteritis and autoimmune arthritis were observed by constructing the model of antigen-induced arthritis (AIA) and colitis induced by dextran sulfate sodium salt (DSS).

RESULTS

We identified peptidase inhibitor 16 (PI16) as a negative regulator of Treg cells. Our findings demonstrate that conditional knock-out of PI16 in Tregs significantly enhances their differentiation and suppressive functions. The conditional knockout of the PI16 gene resulted in a significantly higher abundance of Foxp3 expression (35.12 ± 5.71% vs. 20.00 ± 1.61%, p = 0.034) in iTreg cells induced in vitro compared to wild-type mice. Mice with Treg cell-specific PI16 ablation are protected from autoimmune arthritis (AIA) and dextran sulfate sodium (DSS)-induced colitis development. The AIA model of PI16CKO is characterized by the reduction of joint structure and the attenuation of synovial inflammation and in DSS-induced colitis model, conditional knockout of the PI16 reduce intestinal structural damage. Additionally, we found that the deletion of the PI16 gene in Treg can increase the proportion of Treg (1.46 ± 0.14% vs. 0.64 ± 0.07%, p < 0.0001) and decrease the proportion of Th17 (1.00 ± 0.12% vs. 3.84 ± 0.64%, p = 0.001). This change will enhance the shift of Th17/Treg toward Treg cells in AIA arthritis model (0.71 ± 0.06% vs. 8.07 ± 1.98%, p = 0.003). In DSS-induced colitis model of PI16CKO, the proportion of Treg in spleen was significantly increased (1.40 ± 0.15% vs. 0.50 ± 0.11%, p = 0.003), Th17 (2.18 ± 0.55% vs. 6.42 ± 1.47%, p = 0.017), Th1 (3.42 ± 0.19% vs. 6.59 ± 1.28%, p = 0.028) and Th2 (1.52 ± 0.27% vs. 2.76 ± 0.38%, p = 0.018) in spleen was significantly decreased and the Th17/Treg balance swift toward Treg cells (1.44 ± 0.50% vs. 24.09 ± 7.18%, p = 0.012).

CONCLUSION

PI16 plays an essential role in inhibiting Treg cell differentiation and function. Conditional knock out PI16 gene in Treg can promote the Treg/Th17 balance towards Treg dominance, thereby alleviating the condition. Targeting PI16 may facilitate Treg cell-based therapies for preventing autoimmune diseases and inflammatory diseases. The research provides us with novel insights and future research avenues for the treatment of autoimmune diseases, particularly arthritis and colitis.

High sensitivity of host Helios+/Neuropilin-1+ Treg to pretransplant conditioning hampers development of OX40bright/integrin-β7+ regulatory cells in acute gastrointestinal GvHD

This study sought to compare the behavior of Treg subsets displaying different coexpression patterns of Neuropilin-1 (Nrp1) and Helios, under the influence of gut stress unrelated to hematopoietic stem cell transplantation, pretransplantation conditioning, and posttransplant gastrointestinal acute graft versus host disease (GI-aGvHD). Host CD4+/CD25hi/Foxp3+ Treg cells, identified by flow cytometry, were isolated from various tissues of mice affected by these stressors. Expression of CD25, CTLA-4, CD39, OX40, integrin-β7, LAG3, TGFβ/LAP, granzyme-A, -B, and interleukin-10 was compared in four Treg subsets displaying Helios or Nrp1 only, both or none. Fluorescence-activated cell sorter-sorted Treg subsets, displaying markers affected in a conditioning- and GI-aGVHD-restricted manner, were further investigated by transcriptome profiling and T-cell suppression assays. We found that conditioning by irradiation greatly diminished the relative frequency of Helios+/Nrp1+ Treg, shifting the balance toward Helios-/Nrp1- Treg in the host. Upregulation of integrin-β7 and OX40 occurred in GI-aGvHD-dependent manner in Helios+/Nrp1+ cells but not in Helios-/Nrp1- Treg. Sorted Treg subsets, confirmed to overexpress Nrp1, Helios, OX40, or integrin-β7, displayed superior immunosuppressive activity and enrichment in activation-related messenger RNA transcripts. Our data suggest that conditioning-induced shrinkage of the Nrp1+/Helios+ Treg subset may contribute to the development of GI-GvHD by impairing gut homing and decreasing the efficiency of Treg-mediated immunosuppression.

Co-administration of 1,25-dihydroxyvitamin D3 and infliximab improves colitis in mice by modulating Treg differentiation

Objectives

The combination of TNF-α inhibitors and vitamin D in colitis remains to be elucidated. In the present study, we revealed the benefit of infliximab (IFX) and vitamin D in a mouse model of Ulcerative colitis (UC).

Materials and Methods

A dextran sulfate sodium-induced colitis model was used. The therapeutic effect of the combination was evaluated by symptom and histopathology analysis. The synergistic mechanism was explored by detecting the regulatory effect of the combined therapy on Regulatory T cell (Treg) differentiation.

Results

IFX and 1,25-dihydroxyvitamin D3 (VitD3) synergistically prevented the development of colitis by improving clinical signs, pathological and hematological manifestation, and inhibiting intestinal inflammation (decreasing TNF-α, IL-1β, and IL-6). Co-administration of IFX (2.5 mg/kg) with VitD3 or IFX (5.0 mg/kg) with VitD3 was more effective than administration of IFX (2.5 mg/kg, 5.0 mg/kg). There was no difference in therapeutic effect between IFX (5.0 mg/kg) and VitD3+ IFX (2.5 mg/kg) groups or between the VitD3+IFX (5.0 mg/kg) and VitD3+ Azathioprine (AZA) groups. VitD3 or combination therapy showed more powerful regulation of splenetic Treg differentiation and IL-10 production than IFX alone. Moreover, VitD3 alone or in combination induced higher levels of Foxp3 and IL-10 than IFX in colon tissue. In ulcerative colitis patients, serum VitD3 levels positively correlated with Treg levels.

Conclusion

VitD3 and IFX synergistically inhibit colitis based on their powerful regulation of Treg differentiation. VitD3 combined with IFX is an alternative therapy for patients who are intolerant to standard doses of IFX or combination of IFX and AZA.

Gastrointestinal barrier function, immunity, and neurocognition: The role of human milk oligosaccharide (hMO) supplementation in infant formula

Breastmilk is seen as the gold standard for infant nutrition as it provides nutrients and compounds that stimulate gut barrier, immune, and brain development to the infant. However, there are many instances where it is not possible for an infant to be fed with breastmilk, especially for the full 6 months recommended by the World Health Organization. In such instances, infant formula is seen as the next best approach. However, infant formulas do not contain human milk oligosaccharides (hMOs), which are uniquely present in human milk as the third most abundant solid component. hMOs have been linked to many health benefits, such as the development of the gut microbiome, the immune system, the intestinal barrier, and a healthy brain. This paper reviews the effects of specific hMOs applied in infant formula on the intestinal barrier, including the not-often-recognized intestinal alkaline phosphatase system that prevents inflammation. Additionally, impact on immunity and the current proof for effects in neurocognitive function and the corresponding mechanisms are discussed. Recent studies suggest that hMOs can alter gut microbiota, modulate intestinal immune barrier function, and promote neurocognitive function. The hMOs 2'-fucosyllactose and lacto-N-neotetraose have been found to have positive effects on the development of infants and have been deemed safe for use in formula. However, their use has been limited due to their cost and complexity of synthesis. Thus, although many benefits have been described, complex hMOs and combinations of hMOs with other oligosaccharides are the best approach to stimulate gut barrier, immune, and brain development and for the prevention of disease.

Chlorella vulgaris Modulates Gut Microbiota and Induces Regulatory T Cells to Alleviate Colitis in Mice

Chlorella vulgaris (C. vulgaris) is unicellular green algae consumed worldwide as a functional food. The immune stimulatory function of C. vulgaris is known; however, no study has elucidated its immune regulatory potential and associated microbiome modulation. In the current study, we aimed to validate the immune regulatory role of C. vulgaris mediated through two mechanisms. Initially, we assessed its ability to promote the expansion of the regulatory T cell (Treg) population. Subsequently, we investigated its impact on gut microbiota composition and associated metabolites. The supplementation of C. vulgaris altered the gut microbiota composition, accompanied by increased short-chain fatty acid (SCFAs) production in mice at homeostasis. We later used C. vulgaris in the treatment of a DSS-induced colitis model. C. vulgaris intervention alleviated the pathological symptom of colitis in mice, with a corresponding increase in Treg levels. As C. vulgaris is a safe and widely used food supplement, it can be a feasible strategy to instigate cross-talk between the host immune system and the intestinal flora for the effective management of inflammatory bowel disease (IBD).

Enhancing Regulatory T Cells to Treat Inflammatory and Autoimmune Diseases

Regulatory T cells (Tregs) control immune responses and are essential to maintain immune homeostasis and self-tolerance. Hence, it is no coincidence that autoimmune and chronic inflammatory disorders are associated with defects in Tregs. These diseases have currently no cure and are treated with palliative drugs such as immunosuppressant and immunomodulatory agents. Thereby, there is a great interest in developing medical interventions against these diseases based on enhancing Treg cell function and numbers. Here, we give an overview of Treg cell ontogeny and function, paying particular attention to mucosal Tregs. We review some notable approaches to enhance immunomodulation by Tregs with therapeutic purposes including adoptive Treg cell transfer therapy and discuss relevant clinical trials for inflammatory bowel disease. We next introduce ways to expand mucosal Tregs in vivo using microbiota and dietary products that have been the focus of clinical trials in various autoimmune and chronic-inflammatory diseases.

Flagellin-specific human CAR Tregs for immune regulation in IBD

Regulatory T cell (Treg) therapy is a promising strategy to treat inflammatory bowel disease (IBD). Data from animal models has shown that Tregs specific for intestinal antigens are more potent than polyclonal Tregs at inhibiting colitis. Flagellins, the major structural proteins of bacterial flagella, are immunogenic antigens frequently targeted in IBD subjects, leading to the hypothesis that flagellin-specific Tregs could be an effective cell therapy for IBD. We developed a novel chimeric antigen receptor (CAR) specific for flagellin derived from Escherichia coli H18 (FliC). We used this CAR to confer FliC-specificity to human Tregs and investigated their therapeutic potential. FliC-CAR Tregs were activated by recombinant FliC protein but not a control flagellin protein, demonstrating CAR specificity and functionality. In a humanized mouse model, expression of the FliC-CAR drove preferential migration to the colon and expression of the activation marker PD1. In the presence of recombinant FliC protein in vitro, FliC-CAR Tregs were significantly more suppressive than control Tregs and promoted the establishment of colon-derived epithelial cell monolayers. These results demonstrate the potential of FliC-CAR Tregs to treat IBD and more broadly show the therapeutic potential of CARs targeting microbial-derived antigens.

A Review of Extraintestinal Manifestations & Medication-Induced Myocarditis and Pericarditis in Pediatric Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a systemic disorder where extraintestinal symptoms may involve virtually any organ system. Of these extraintestinal symptoms, those involving the heart are relatively rare but associated with significant morbidity. We reviewed the existing literature on noninfectious myocarditis and pericarditis in the pediatric IBD population, including extraintestinal manifestations (EIMs) of IBD and extraintestinal complications (EICs) from medication. We focused on the incidence, presentation, diagnosis, treatment, and outcomes for timely diagnosis and management of these potentially deadly diseases. In addition, we aim to identify and highlight the gaps in current knowledge for future studies and investigations.

The effect of inulin-type fructans on the intestinal immune function of antibiotic-treated mice

This study aimed to evaluate the effect of supplementation with inulin-type fructans (ITFs) on the intestinal immune function in the context of dysbiosis resulting from antibiotic cocktail (ABx) treatment. BALB/c mice (8-9 weeks of age) were treated with an ABx for 3 weeks and then allowed to recover spontaneously or with ITF supplementation (5%) for 4 weeks. Our results showed that ABx treatment can induce gut microbiota dysbiosis and intestinal inflammation in mice. After 4 weeks of recovery, ITF supplementation restored the composition of the intestinal microbial community. However, compared with spontaneous recovery, ITF supplementation delayed inflammation recovery in the intestine and upregulated diamine oxidase (DAO) activity and increased lipopolysaccharide (LPS) content in serum. In addition, ITF supplementation delayed the regulatory T (Treg) cell and B cell recovery in the lamina propria (LP). Furthermore, compared with spontaneous recovery, ITF supplementation inhibited the relative expression of certain proinflammatory genes, such as for inducible nitric oxide synthase (iNOS) and tumour necrosis factor α (Tnf-α), in the colon, but it reduced the secretion of the anti-inflammatory mediator transforming growth factor β1 (TGF-β1) in serum, reduced the secretion of secretory immunoglobulin A (SIgA) in the colon and promoted the secretion of the proinflammatory cytokine interleukin (IL)-17A. In conclusion, these data supported the hypothesis that the influence of ITFs on the host's intestinal status is not always beneficial in the context of ABx-induced biological disorder. However, the significance of these findings needs to be determined by advanced studies KEY POINTS: • ITFs did not promote the recovery of microbial community composition. • ITFs delayed the recovery of ABx-induced colonic inflammation. • ITFs reduced the secretion of TGF-β1 and SIgA. • ITFs delayed the recovery of Treg and B cells in the LP.

Collagenous Colitis Mucosa Is Characterized by an Expansion of Nonsuppressive FoxP3+ T Helper Cells

BACKGROUND AND AIM

Increased frequencies of T regulatory (Treg) cells, key players in immune regulation, have been reported in inflammatory bowel diseases, including collagenous colitis (CC). However, traditional Treg identification techniques might have misinterpreted the frequencies of Treg cells in CC. Thus, we investigated the presence of genuine Treg cells in CC.

METHODS

Treg cells were analyzed in mucosal and peripheral blood samples of CC patients before and during treatment with the corticosteroid drug budesonide and in healthy controls. Samples were analyzed by flow cytometry by classifying CD3+CD4+ cells as activated FoxP3highCD45RA- Treg cells, resting FoxP3dimCD45RA+ Treg cells, and nonsuppressive FoxP3dimCD45RA- T helper cells. Traditional gating strategies that classified Treg cells as CD25highCD127low, FoxP3+CD127low, and CD4+CD25+FoxP3+ were also used to facilitate comparison with previous studies.

RESULTS

Activated and resting Treg cell frequencies did not change in active CC mucosa or peripheral blood and were not affected by budesonide treatment. Instead, nonsuppressive FoxP3dimCD45RA- T helper cells were increased in active CC mucosa, and budesonide helped restore them to normal levels. In contrast, traditional Treg cell gating strategies resulted in increased Treg cell frequencies in active CC mucosa. No alterations were found in peripheral blood samples, independently of patient treatment or gating techniques.

CONCLUSION

Previously reported increase of Treg cells is a result of incomplete Treg phenotyping, which included nonsuppressive FoxP3dimCD45RA- T helper cells. Because budesonide did not affect Treg percentage, its therapeutic effect in CC might involve alternative mechanisms.

Translating Treg Therapy for Inflammatory Bowel Disease in Humanized Mice

Crohn's disease and ulcerative colitis, two major forms of inflammatory bowel disease (IBD) in humans, afflicted in genetically predisposed individuals due to dysregulated immune response directed against constituents of gut flora. The defective immune responses mounted against the regulatory mechanisms amplify and maintain the IBD-induced mucosal inflammation. Therefore, restoring the balance between inflammatory and anti-inflammatory immunepathways in the gut may contribute to halting the IBD-associated tissue-damaging immune response. Phenotypic and functional characterization of various immune-suppressive T cells (regulatory T cells; Tregs) over the last decade has been used to optimize the procedures for in vitro expansion of these cells for developing therapeutic interventional strategies. In this paper, we review the mechanisms of action and functional importance of Tregs during the pathogenesis of IBD and modulating the disease induced inflammation as well as role of mouse models including humanized mice repopulated with the human immune system (HIS) to study the IBD. "Humanized" mouse models provide new tools to analyze human Treg ontogeny, immunobiology, and therapy and the role of Tregs in developing interventional strategies against IBD. Overall, humanized mouse models replicate the human conditions and prove a viable tool to study molecular functions of human Tregs to harness their therapeutic potential.

Phytochemicals as regulators of Th17/Treg balance in inflammatory bowel diseases

Inflammatory bowel disease (IBD) is a chronic inflammatory intestinal disorder that is difficult to cure and characterized by periods of relapse. To face the challenges of limited treatment strategies and drawbacks of conventional medications, developing new and promising strategies as well as safe and effective drugs for treatment of IBD has become an urgent demand for clinics. The imbalance of Th17/Treg is a crucial event for the development of IBD, and studies have verified that correcting the imbalance of Th17/Treg is an effective strategy for preventing and treating IBD. Recently, a growing body of studies has indicated that phytochemicals derived from natural products are potent regulators of Th17/Treg, and exert preferable protective benefits against colonic inflammation. In this review, the great potential of anti-colitis agents derived from natural products through targeting Th17/Treg cells and their action mechanisms for the treatment or prevention of IBD in recent research is summarized, which may help further the development of new drugs for IBD treatment.

Ssu72 is a T-cell receptor-responsive modifier that is indispensable for regulatory T cells

The homeostatic balance between effector T cells and regulatory T cells (Tregs) is crucial for adaptive immunity; however, epigenetic programs that inhibit phosphorylation to regulate Treg development, peripheral expression, and suppressive activity are elusive. Here, we found that the Ssu72 phosphatase is activated by various T-cell receptor signaling pathways, including the T-cell receptor and IL-2R pathways, and localizes at the cell membrane. Deletion of Ssu72 in T cells disrupts CD4+ T-cell differentiation into Tregs in the periphery via the production of high levels of the effector cytokines IL-2 and IFNγ, which induce CD4+ T-cell activation and differentiation into effector cell lineages. We also found a close correlation between downregulation of Ssu72 and severe defects in mucosal tolerance in patients. Interestingly, Ssu72 forms a complex with PLCγ1, which is an essential effector molecule for T-cell receptor signaling as well as Treg development and function. Ssu72 deficiency impairs PLCγ1 downstream signaling and results in failure of Foxp3 induction. Thus, our studies show that the Ssu72-mediated cytokine response coordinates the differentiation and function of Treg cells in the periphery.

Preoperatively predicting the pathological types of acute appendicitis using machine learning based on peripheral blood biomarkers and clinical features: a retrospective study

Background

This study aimed to establish machine learning models for preoperative prediction of the pathological types of acute appendicitis.

Methods

Based on histopathology, 136 patients with acute appendicitis were included and divided into three types: acute simple appendicitis (SA, n=8), acute purulent appendicitis (PA, n=104), and acute gangrenous or perforated appendicitis (GPA, n=24). Patients with SA/PA and PA/GPA were divided into training (70%) and testing (30%) sets. Statistically significant features (P<0.05) for pathology prediction were selected by univariate analysis. According to clinical and laboratory data, machine learning logistic regression (LR) models were built. Area under receiver operating characteristic curve (AUC) was used for model assessment.

Results

Nausea and vomiting, abdominal pain time, neutrophils (NE), CD4⁺ T cell, helper T cell, B lymphocyte, natural killer (NK) cell counts, and CD4⁺/CD8⁺ ratio were selected features for the SA/PA group (P<0.05). Nausea and vomiting, abdominal pain time, the highest temperature, CD8⁺ T cell, procalcitonin (PCT), and C-reactive protein (CRP) were selected features for the PA/GPA group (P<0.05). By using LR models, the blood markers can distinguish SA and PA (training AUC =0.904, testing AUC =0.910). To introduce additional clinical features, the AUC for the testing set increased to 0.926. In the PA/GPA prediction model, AUC with blood biomarkers was 0.834 for the training and 0.821 for the testing set. Combining with clinical features, the AUC for the testing set increased to 0.854.

Conclusions

Peripheral blood biomarkers can predict the pathological type of SA from PA and GPA. Introducing clinical symptoms could further improve the prediction performance.

Value of cord blood Treg population properties and function-associated characteristics for predicting allergy development in childhood

Allergic diseases represent some of the most common immunological disorders with high clinical and economic impact. Despite intensive research, there are still few universally accepted and reliable biomarkers capable of predicting their development at an early age. There is therefore a pressing need for identification of potential predictive factors and validation of their prognostic value by correlating them with allergy development. Dysbalance of the branches of immune response, most often excessive Th2 polarization, is the principal cause of allergic diseases. Regulatory T cells (Treg) are a crucial population for the timely establishment of physiological immune polarization and induction and maintenance of tolerance against environmental antigens. This makes them a potentially promising candidate for an early marker predicting allergy development. In our study, we analysed samples of cord blood of children of allergic mothers and children of healthy mothers by flow cytometry and retrospectively correlated the data with clinical allergy status of the children at the age of 6 to 10 years. Studied parameters included cord blood Treg population proportions and functional properties - intracellular presence of IL-10 and TGF-b, MFI of FoxP3. We observed higher percentage of Tregs in cord blood of children who did not develop allergy compared with allergic children. Further, we found higher numbers of IL-10+ Tregs in cord blood of healthy children of healthy mothers than in cord blood of children of allergic mothers and decreased TGF-b+ cord blood Tregs in the group of allergic children of allergic mothers compared to all other groups.

Lactoferrin-mediated macrophage targeting delivery and patchouli alcohol-based therapeutic strategy for inflammatory bowel diseases

Inflammatory bowel diseases (IBD) are the incurable chronic recurrent gastrointestinal disorders and currently lack in safe and effective drugs. In this study, patchouli alcohol, a main active compound of traditional Chinese herb patchouli, was developed into biomimetic liposomes for macrophage-targeting delivery for IBD treatment. The developed lactoferrin-modified liposomes (LF-lipo) can specifically bind to LRP-1 expressed on the activated colonic macrophages and achieve cell-targeting anti-inflammatory therapy. LF-lipo reduced the levels of inflammatory cytokines and ROS and suppressed the MAPK/NF-κB pathway. LF-lipo also suppressed the formation of NLRP3 inflammasome and the consequent IL-1β activation. LF-lipo showed improved therapeutic efficacy in a DSS-induced colitis murine model, evidenced by the reduced disease activity index, the improved colon functions, and the downregulated inflammatory cytokines in the colon. LF-lipo provided an effective and safe macrophage-targeting delivery and therapeutic strategy for addressing the unmet medical need in IBD management.

Immunohistochemical Findings in Idiopathic Inflammatory Bowel Disease in Nine Cats

Inflammatory bowel disease is a term referring to a clinical condition characterized by recurrent/persistent gastrointestinal signs, which cannot be diagnosed only through histological findings, being an elimination diagnosis and needing therefore the previous exclusion of all other possible causes of gastrointestinal signs. The aim of the present study was to compare the expression of different cytokines on endoscopic biopsy samples of the small and large intestine of cats suffering from inflammatory bowel disease and healthy controls, by immunohistochemistry evaluation. Nine cats referred for chronic gastrointestinal signs to the Gastroenterology Service, Teaching Hospital, Faculty of Veterinary Sciences, University of Buenos Aires, were included. After being administered with antiparasitic drugs and after running complete laboratory exams, abdominal ultrasonography, etc., upper and lower gastrointestinal endoscopy with biopsy samplings for histopathology and immunohistochemistry was then performed. Controls were represented by archived samples from healthy cats (University of Camerino, Italy, Veterinary Pathology Unit Archive). On biopsy samples, the immunohistochemistry expression of the following antibodies was evaluated: TGF-β, CD3+, FoxP3+, TNF-α, IL-1β, IL-10, IL-12, and Th-17+. Statistic analysis was performed with the nonparametric Mann-Whitney test and with Spearman test, considering significant $p<0.05$ . TNF-α, IL-1β, IL-12, and CD3+ were significantly differently expressed between cats suffering from inflammatory bowel disease and controls, while no differences were found regarding TGF-β, IL-10, and FOXP3. A positive correlation was also found between proinflammatory cytokines and proinflammatory cytokines plus lymphocytes that were at the same time related to IL-10 and TGF-β. On the other hand, a negative correlation was found between proinflammatory and regulatory cytokines. Our results suggest an imbalance in the immune response which may play a role in the etiopathogenesis of feline inflammatory bowel disease.

Decreased Frequency of Intestinal CD39+ γδ+ T Cells With Tissue-Resident Memory Phenotype in Inflammatory Bowel Disease

The ectoenzymes CD39 and CD73 play a major role in controlling tissue inflammation by regulating the balance between adenosine triphosphate (ATP) and adenosine. Still, little is known about the role of these two enzymes and ATP and its metabolites in the pathophysiology of inflammatory bowel disease (IBD). We isolated mononuclear cells from peripheral blood and lamina propria of the large intestine of patients diagnosed with IBD and of healthy volunteers. We then comprehensively analyzed the CD39 and CD73 expression patterns together with markers of activation (HLA-DR, CD38), differentiation (CCR7, CD45RA) and tissue-residency (CD69, CD103, CD49a) on CD4⁺, CD8⁺, γδ⁺ T cells and mucosa-associated invariant T cells using flow cytometry. CD39 expression levels of γδ⁺ and CD8⁺ T cells in lamina propria lymphocytes (LPL) were much higher compared to peripheral blood mononuclear cells. Moreover, the frequency of CD39⁺ CD4⁺ and CD8⁺, but not γδ⁺ LPL positively correlated with T-cell activation. The frequency of CD39⁺ cells among tissue-resident memory LPL (Trm) was higher compared to non-Trm for all subsets, confirming that CD39 is a marker for the tissue-resident memory phenotype. γδ⁺ Trm also showed a distinct cytokine profile upon stimulation – the frequency of IFN-γ⁺ and IL-17A⁺ cells was significantly lower in γδ⁺ Trm compared to non-Trm. Interestingly, we observed a decreased frequency of CD39⁺ γδ⁺ T cells in IBD patients compared to healthy controls (p = 0.0049). Prospective studies need to elucidate the exact role of this novel CD39⁺ γδ⁺ T-cell population with tissue-resident memory phenotype and its possible contribution to the pathogenesis of IBD and other inflammatory disorders.

Histone deacetylases as targets in autoimmune and autoinflammatory diseases

Reversible lysine acetylation of histones is a key epigenetic regulatory process controlling gene expression. Reversible histone acetylation is mediated by two opposing enzyme families: histone acetyltransferases (HATs) and histone deacetylases (HDACs). Moreover, many non-histone targets of HATs and HDACs are known, suggesting a crucial role for lysine acetylation as a posttranslational modification on the cellular proteome and protein function far beyond chromatin-mediated gene regulation. The HDAC family consists of 18 members and pan-HDAC inhibitors (HDACi) are clinically used for the treatment of certain types of cancer. HDACi or individual HDAC member-deficient (cell lineage-specific) mice have also been tested in a large number of preclinical mouse models for several autoimmune and autoinflammatory diseases and in most cases HDACi treatment results in an attenuation of clinical disease severity. A reduction of disease severity has also been observed in mice lacking certain HDAC members. This indicates a high therapeutic potential of isoform-selective HDACi for immune-mediated diseases. Isoform-selective HDACi and thus targeted inactivation of HDAC isoforms might also overcome the adverse effects of current clinically approved pan-HDACi. This review provides a brief overview about the fundamental function of HDACs as epigenetic regulators, highlights the roles of HDACs beyond chromatin-mediated control of gene expression and summarizes the studies showing the impact of HDAC inhibitors and genetic deficiencies of HDAC members for the outcome of autoimmune and autoinflammatory diseases with a focus on rheumatoid arthritis, inflammatory bowel disease and experimental autoimmune encephalomyelitis (EAE) as an animal model of multiple sclerosis.

Spontaneous onset of TNFα-triggered colonic inflammation depends on functional T lymphocytes, S100A8/A9 alarmins, and MHC H-2 haplotype

Recently, we established a doxycycline-inducible human tumor necrosis factor alpha (TNFα)-transgenic mouse line, ihTNFtg. Non-induced young and elderly mice showed low but constitutive expression of hTNFα due to promoter leakiness. The persistently present hTNFα stimulated endogenous pro-inflammatory mouse mS100A8/A9 alarmins. Secreted mS100A8/A9 in turn induced the expression and release of mouse mTNFα. The continuous upregulation of pro-inflammatory mTNFα and mS100A8/A9 proteins, due to their mutual expression dependency, gradually led to increased levels in colon tissue and blood. This finally exceeded the threshold levels tolerated by the healthy organism, leading to the onset of intestinal inflammation. Here, recombinant hTNFα functioned as an initial trigger for the development of chronic inflammation. Crossing ihTNFtg mice with S100A9^KO mice lacking active S100A8/A9 alarmins or with Rag1^KO mice lacking T and B lymphocytes completely abrogated the development of colonic inflammation, despite the still leaky hTNFα promoter. Furthermore, both the intensity of the immune response and the strength of immunosuppressive Treg induction was found to depend on the major histocompatibility complex (MHC) genetic composition. In summary, the onset of intestinal inflammation in elderly mice depends on at least four factors that have to be present simultaneously: TNFα upregulation, S100A8/A9 protein expression, functional T lymphocytes and genetic composition, with the MHC haplotype being of central importance. Only joint action of these factors leads to chronic intestinal inflammation, while absence of any of these determinants abrogates the development of the autoimmune disorder. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Different Expression Pattern of TIM-3 and Galectin-9 Molecules by Peripheral and Peritoneal Lymphocytes in Women with and without Endometriosis

Endometriosis is a gynecological condition that is associated with chronic pelvic inflammation, pain, and infertility. Although substantial evidence supports that immunological alterations contribute to its pathogenesis and we previously posed a pivotal role of Galectin-9 (Gal-9) in this disorder, the involvement of the TIM-3/Gal-9 pathway in the development of endometriosis-associated immunological abnormalities is not yet known. In the present study, multicolor flow cytometry was used to compare the immunophenotype and cell surface expression of TIM-3 and Gal-9 molecules on peripheral blood (PB) and peritoneal fluid (PF) lymphocytes of women with and without endometriosis. We found an altered distribution of different lymphocyte subpopulations, a markedly decreased TIM-3 labeling on all T and NK subsets and a significantly increased Gal-9 positivity on peripheral CD4+ T and Treg cells of the affected cohort. Furthermore, a significantly increased TIM-3 expression on CD4+T-cells and elevated Gal-9 labeling on all T and NK subsets was also revealed in the PF of the examined patients. In conclusion, our results suggest a persistent activation and disturbed TIM-3/Gal-9-dependent regulatory function in endometriosis, which may be involved in the impaired immune surveillance mechanisms, promotes the survival of ectopic lesions, and aids the evolution of reproductive failures in endometriosis.

Intake of dietary fibre, red and processed meat and risk of late-onset Chronic Inflammatory Diseases: A prospective Danish study on the "diet, cancer and health" cohort

Background: Human and animal studies support the involvement of diet in the development of CID -chronic inflammatory diseases such as inflammatory bowel disease, psoriasis, rheumatoid arthritis, psoriatic arthritis, and multiple sclerosis. Objective: This cohort study aimed to investigate the association between intake of fibre, red and processed meat, and occurrence of late-onset CID (50+ years of age) in the DCH: Danish Diet, Cancer and Health cohort. We hypothesised that risk of late-onset CID would be lower among those with high intake of fibre and/or low intake of meat compared to individuals with low fibre and/or high meat intake. Methods: The DCH recruited 56,468 individuals, aged 50-64 years, between 1993 and 1997. At recruitment, diet intake was registered using food frequency questionnaires as well as lifestyle factors in 56,075 persons. Exposure variables were generated as sex-adjusted tertiles of fibre and meat (g/day). Development of CIDs was identified in national registries. Hazard ratios (HR) of late-onset CIDs (adjusted for age, sex, energy intake, alcohol, smoking, education, comorbidity, and civil status) were estimated for all three exposure variables. Results: During follow-up of 1,123,754 years (median (Interquartile range) = 22.2 (20.1-23.1)), 1,758 (3.1%) participants developed at least one CID. The adjusted HRs for developing CID (low fibre 1.04 [0.89-1.22] and medium fibre 1.04 [0.91-1.18] (high fibre as reference), and medium meat 0.96 [0.86-1.09] and high meat 0.94 [0.82-1.07] (low meat as reference)) or the individual diseases were not statistically significant. Conclusion: This large study did not support that a high intake of fibre and/or a low intake of meat had a high impact on the risk of late-onset CID.

Distribution of regulatory T cells in inflammatory colorectal polyps of miniature dachshunds

Inflammatory colorectal polyp (ICRP) is an emerging disease in Miniature Dachshunds (MDs). Animals with this disease exhibit multiple polyps with severe neutrophil infiltration that respond to immunosuppressive therapy. Macrophages in polypoid lesions have been described to play an important role in neutrophil infiltration in the lesion by producing IL-8. In contrast, IL-10, an anti-inflammatory cytokine, was also reported to be upregulated in polypoid lesions, but its significance in the pathogenesis of ICRP has not been clarified. Regulatory T cells (Tregs) are the main source of IL-10 production and contribute to the maintenance of intestinal homeostasis. Therefore, the objective of this research was to compare the distribution of Tregs in polypoid lesions of ICRPs and the association between the distribution and expression of pro- or anti-inflammatory cytokines. Tissue biopsy specimens of polypoid lesions were collected from 28 MDs with ICRP. Those of macroscopically non-polypoid colonic mucosa from 24 MDs with ICRPs and 21 control dogs were further included as controls. Real-time quantitative polymerase chain reaction was used to quantify gene expression of IL-1β, IL-4, IL-6, IL-8, IL-10, IL-17, IL-22, IFN-γ, TNF-α, TGF-β, and forkhead box protein P3 (Foxp3) in each tissue sample. The numbers of Foxp3-positive cells (Tregs) and ionized calcium binding adapter molecule 1 (Iba-1)-positive cells (macrophages) were determined by immunohistochemistry. The gene expression of IL-1β, IL-6, IL-8, TNF-α, IFN-γ, IL-17, IL-10, TGF-β, and Foxp3 was significantly upregulated in polypoid lesions relative to control levels. The numbers of Foxp3-positive Tregs and Iba-1-positive macrophages were significantly increased in polypoid lesions compared to those in the non-polypoid colonic mucosa of MDs with ICRPs and control dogs. The upregulation of IL-10 was moderately correlated with the distribution of Tregs in polypoid lesions from MDs with ICRPs. In addition, the relative upregulation of IL-1β, IL-6, and IL-8 in polypoid lesions, compared to expression in non-polypoid colonic mucosa of MDs with ICRPs, was significantly greater than that of IL-10. These results indicate that increases in Treg numbers and anti-inflammatory cytokines in polypoid lesions comprise reactive changes in response to the inflammation, which warrants further investigation.

pVAX1-A20 alleviates colitis in mice by promoting regulatory T cells

AIM

To investigate whether the intrarectal administration of the ubiquitin E3 ligase A20 (A20) attenuates intestinal inflammation and influences regulatory T cells in experimental colitis.

METHODS

A dextran sulfate sodium induced chronic colitis mouse model was established. The symptoms and manifestations of colitis and the severity of colonic mucosal inflammation were evaluated. The protective role of A20 expression in the intestine was analyzed after the administration of a pVAX1-A20 recombinant eukaryotic vector, which was encapsulated into poly(L-lactide-co-glycolide) as a nanoparticle.

RESULTS

pVAX1-A20 administration markedly ameliorated colonic tissue damage and reduced intestinal inflammation via the suppression of the mucosal mitogen-activated protein kinase and nuclear factor (NF)-κB signaling cascade. Furthermore, pVAX1-A20 promoted the splenic regulatory T cell population and forkhead box P3 expression in colonic tissue.

CONCLUSION

A20 plays a key role in the regulation of intestinal inflammation and that the overexpression of A20 in the intestine protects mice from dextran sulfate sodium induced chronic colitis.

Impact of red meat, processed meat and fibre intake on risk of late-onset chronic inflammatory diseases: prospective cohort study on lifestyle factors using the Danish 'Diet, Cancer and Health' cohort (PROCID-DCH): protocol

INTRODUCTION

Chronic inflammatory diseases (CIDs) (Crohn's disease, ulcerative colitis, psoriasis, psoriatic arthritis, rheumatoid arthritis and multiple sclerosis) are diseases of the immune system that have some shared genetic and environmental predisposing factors, but still few studies have investigated the effects of lifestyle on disease risk of several CIDs. The primary aim of this prospective cohort study is to investigate the impact of fibre, red meat and processed meat on risk of late-onset CID, with the perspective that results of this study can contribute in supporting future diet recommendations for effective personalised prevention.

METHODS AND ANALYSIS

The study will use data from 57 053 persons from the prospective Danish cohort study 'Diet, Cancer and Health' together with National Health Registry data. The follow-up period is from December 1993 to December 2018. Questionnaire data on diet and lifestyle were collected at entry to the Diet, Cancer and Health study. The outcome CID is defined as having a diagnosis of one of the CIDs registered in the National Patient Registry or, for multiple sclerosis, in the Danish Multiple Sclerosis Registry during follow-up and being treated with a drug used for the specific disease. The major outcome of the analyses will be to detect variability in risk of late onset of any CID and, if power allows, disease risk of late onset of each CID diagnosis between persons with different fibre and red meat, and processed meat intake. The outcome will be adjusted for age, sex, body mass index, physical activity, energy, alcohol, fermented dairy products, education, smoking status, hormone replacement therapy and comorbidity.

ETHICS AND DISSEMINATION

The study is approved by the Danish Data Protection Agency (2012-58-0018). The core study is an open register-based cohort study. The study does not need approval from the Ethics committee or Institutional Review Board by Danish law. Study findings will be disseminated through peer-reviewed journals, patient associations and presentations at international conferences.

TRIAL REGISTRATION NUMBER

NCT03456206; Post-results.

Hesperidin Protects Against Intestinal Inflammation by Restoring Intestinal Barrier Function and Up-Regulating Treg Cells

SCOPE

Hesperidin is an important natural phenolic compound and is considered beneficial to health. The purpose of this study is to investigate the protective effects of hesperidin on DSS-induced colitis in mice and Caco-2 cells.

METHODS

The DSS-induced colitis mice are assigned to 10, 20, and 40 mg kg^-g hesperidin diets after DSS treatment. For in vitro experiments, Caco-2 cells are treated with TNF-α/ IFN-γ for 48 h without or with hesperidin.

RESULTS

Hesperidin supplementation ameliorates DSS-induced colitis. Specifically, hesperidin ameliorates intestinal inflammation through decreasing MDA activity and enhancing SOD and GSH activities. Hesperidin also obviously upregulates Nrf2 antioxidant pathway and increases the protein expression of HO-1 and NQO1. Additionally, hesperidin significantly reduces the levels of inflammatory factors and increases the levels of anti-inflammatory factors in the colon tissues. Further analysis shows that hesperidin can improve the expression of tight junction proteins and intestinal permeability, as well as increases the Treg population. In Caco-2 cells, it is shown that hesperidin prevents TNF-α/IFN-γ-induced reduction in TEER and morphological disruption. Moreover, hesperidin also decreases the epithelial permeability and suppresses proinflammatory responses.

CONCLUSION

Hesperidin can protect against intestinal inflammation via enhanced Nrf2 antioxidant pathway, increases the Treg population, and restores intestinal barrier function.

Vasoactive intestinal peptide is required in the maintenance of immune regulatory competency of immune regulatory monocytes

Dysfunction of the immune regulatory system plays an important role in the pathogenesis of rheumatoid arthritis (RA). Vasoactive intestinal peptide (VIP) has multiple bioactivities. This study aims to investigate the role of VIP in the maintenance of the immune regulatory capacity of monocytes (Mos). Human peripheral blood samples were collected from RA patients and healthy control (HC) subjects. Mos and CD14⁺ CD71^- CD73⁺ CD25⁺ regulatory Mos (RegMos) were isolated from the blood samples and characterized by flow cytometry. A rat RA model was developed to test the role of VIP in the maintenance of the immune regulatory function of Mos. The results showed that RegMos of HC subjects had immune suppressive functions. RegMos of RA patients expressed less interleukin (IL)-10 and showed an incompetent immune regulatory capacity. Serum levels of VIP were lower in RA patients, which were positively correlated with the expression of IL-10 in RegMos. In-vitro experiments showed that the IL-10 mRNA decayed spontaneously in RegMos, which could be prevented by the presence of VIP in the culture. VIP suppressed the effects of tristetraprolin (TTP) on inducing IL-10 mRNA decay in RegMos. Administration of VIP inhibited experimental RA in rats through restoring the IL-10 expression in RegMos. RegMos have immune suppressive functions. VIP is required in maintaining IL-10 expression in RegMos. The data suggest that VIP has translational potential in the treatment of immune disorders such as RA.

Subclinical Nasal and Lung Lymphocytosis in Ulcerative Colitis

Background

Extraintestinal manifestations are common in ulcerative colitis (UC). Data regarding pulmonary and nasal mucosa involvement are sparse.

Objectives

The aim of the study was to evaluate, by using induced sputum (IS) and nasal cytology (NC), the cytological pattern of the lung and nose in patients with UC.

Materials and Methods

We enrolled 15 consecutive subjects from the outpatient department with a recent diagnosis of UC. On the same day of enrollment, we performed a global spirometry, including a lung diffusing capacity test, IS analysis, and evaluation of NC.

Results

IS analysis showed an increase in lymphocytes in UC patients when compared to those of controls (2.8 ± 0.9 vs. 0.2 ± 0.4%; p < 0.01). NC showed a similar increase in lymphocytes (12.5 ± 5.30 vs. 3.5 ± 4.0%; p < 0.01). We found a positive correlation between lymphocyte counts in IS and NC (r = 0.775; p < 0.001) and between lymphocytes in IS and NC and grade of intestinal inflammation (r = 0.603, p = 0.015; r = 0.60, p = 0.013).

Conclusions

Our data demonstrated that UC patients may have a subclinical nasal and lung lymphocytosis.

Disruption in the Regulation of Immune Responses in the Placental Subtype of Preeclampsia

Preeclampsia is a pregnancy-specific disorder, of which one of its major subtypes, the placental subtype is considered a response to an ischemic placental environment, impacting fetal growth and pregnancy outcome. Inflammatory immune responses have been linked to metabolic and inflammatory disorders as well as reproductive failures. In healthy pregnancy, immune regulatory mechanisms prevent excessive systemic inflammation. However, in preeclampsia, the regulation of immune responses is disrupted as a result of aberrant activation of innate immune cells and imbalanced differentiation of T-helper cell subsets creating a cytotoxic environment in utero. Recognition events that facilitate immune interaction between maternal decidual T cells, NK cells, and cytotrophoblasts are considered an indirect cause of the incomplete remodeling of spiral arteries in preeclampsia. The mechanisms involved include the activation of immune cells and the subsequent secretion of cytokines and placental growth factors affecting trophoblast invasion, angiogenesis, and eventually placentation. In this review, we focus on the role of excessive systemic inflammation as the result of a dysregulated immune system in the development of preeclampsia. These include insufficient control of inflammation, failure of tolerance toward paternal antigens at the fetal-maternal interface, and subsequent over- or insufficient activation of immune mediators. It is also possible that external stimuli, such as bacterial endotoxin, may contribute to the excessive systemic inflammation in preeclampsia by stimulating the release of pro-inflammatory cytokines. In conclusion, a disrupted immune system might be a predisposing factor or result of placental oxidative stress or excessive inflammation in preeclampsia. Preeclampsia can thus be considered a hyperinflammatory state associated with defective regulation of the immune system proposed as a key element in the pathological events of the placental subtype of this disorder.

Pleiotropic Immune Functions of Chemokine Receptor 6 in Health and Disease

C-C chemoattractant cytokine (chemokine) receptor 6 (CCR6) and its exclusive binding molecule CCL20 is an extremely important chemokine receptor-ligand pair which controls cell migration and immune induction during inflammatory disease. Not many scientific studies have been undertaken to study its immune mechanisms in detail, but its unique contribution to steady state cell chemotaxis in upholding immune tolerance and regulating immune homeostasis during inflammation is evident in multiple systems in the human body, including skin, liver, lung, kidney, brain, eye, joints, gonads and the gut. The role of CCR6 is constitutively expressed as a series of much debilitating severe inflammatory and autoimmune diseases, Human Immunodeficiency Virus (HIV) and cancer metastasis. CD4⁺ T cells, the central organizers of adaptive immunity, are stringently mobilized by the CCR6/CCL20 axis also induced by cytokines and a host of other factors in a carefully executed immune modulation scenario, to bring about a delicate balance between inflammation inducing T_H17 cells and regulatory T_reg cells. Although the exact immune regulatory role is not elucidated as yet, the CCR6/CCL20 axis is implicated as a front runner which determines the polarization of T_H17 and regulatory T_reg cells, upon which depends the resolution or progression of many debilitating disorders. This review therefore aims at emphasizing the pleiotropic significance of the chemokines CCR6 and CCL20 in immunologic function in multiple organ systems, thereby hoping to accentuate its value in future therapeutic modalities.

Anti-inflammatory intravenous immunoglobulin (IVIg) suppresses homeostatic proliferation of B cells

An intravenous injection of plasma-derived immunoglobulins is used for the treatment of severe infectious and autoimmune disorders. Despite of its clinical efficacy, precise mechanisms by which intravenous immunoglobulin (IVIg) suppresses proinflammatory immune response are still enigmatic. Here, we provide in vitro evidence that IVIg inhibits homeostatic proliferation of B cells accompanied by induction of their cell aggregation. The IVIg-driven suppression of B cell proliferation and induction of cell aggregation are both unaffected by treatment with a neutralizing antibody against low-affinity Fc receptors for IgG (CD16/FcγRIII and CD32/FcγRII), known cell surface ligands for IVIg. Our observations propose a new immunosuppressive action of IVIg, which directly acts on steady-state B cells to suppress their homeostatic expansion.

Regulatory T cells with superior immunosuppressive capacity emigrate from the inflamed colon to draining lymph nodes

Foxp3⁺ Regulatory T cells (Tregs) play a critical role in the maintenance of colon homeostasis. Here we utilized photoconvertible KikGR mice to track immune cells from the caecum and ascending (proximal) colon in the steady state and DSS-induced colitis. We found that Tregs from the proximal colon (colonic migratory Tregs) migrated exclusively to the distal part of mesenteric lymph nodes (dMLN) in an S1PR1-dependent process. In the steady state, colonic migratory CD25⁺ Tregs expressed higher levels of CD103, ICOS, LAG3 and CTLA-4 in comparison with pre-existing LN Tregs. Intestinal inflammation led to accelerated Treg replacement in the colon, bidirectional Treg migration from the colon to dMLN and vice versa, as well as increases in Treg number, proliferation and expression of immunosuppressive molecules. This was especially apparent for CD25 very high Tregs induced in colitis. Furthermore, colonic migratory Tregs from the inflamed colon included more interleukin (IL)-10 producing cells, and demonstrated greater inhibition of T-cell proliferation in comparison with pre-existing LN Tregs. Thus, our results suggest that Tregs with superior immunosuppressive capacity are increased both in the colon and dMLN upon inflammation. These Tregs recirculate between the colon and dMLN, and are likely to contribute to the downregulation of intestinal inflammation.

Mechanism-Based Strategies for the Management of Autoimmunity and Immune Dysregulation in Primary Immunodeficiencies

A broad spectrum of autoimmunity is now well described in patients with primary immunodeficiencies (PIDs). Management of autoimmune disease in the background of PID is particularly challenging given the seemingly discordant goals of immune support and immune suppression. Our growing ability to define the molecular underpinnings of immune dysregulation has facilitated novel targeted therapeutics. This review focuses on mechanism-based treatment strategies for the most common autoimmune and inflammatory complications of PID including autoimmune cytopenias, rheumatologic disease, and gastrointestinal disease. We aim to provide guidance regarding the rational use of these agents in the complex PID patient population.

The Intricate Link among Gut "Immunological Niche," Microbiota, and Xenobiotics in Intestinal Pathology

Inflammatory bowel diseases (IBDs) are diseases characterized by various degrees of inflammation involving the gastrointestinal tract. Ulcerative colitis and Crohn's disease are characterized by a dysregulated immune response leading to structural gut alterations in genetically predisposed individuals. Diverticular disease is characterized by abnormal immune response to normal gut microbiota. IBDs are linked to a lack of physiological tolerance of the mucosal immune system to resident gut microbiota and pathogens. The disruption of immune tolerance involves inflammatory pathways characterized by an unbalance between the anti-inflammatory regulatory T cells and the proinflammatory Th1/Th17 cells. The interaction among T cell subpopulations and their related cytokines, mediators of inflammation, gut microbiota, and the intestinal mucosa constitute the gut “immunological niche.” Several evidences have shown that xenobiotics, such as rifaximin, can positively modulate the inflammatory pathways at the site of gut immunological niche, acting as anti-inflammatory agents. Xenobiotics may interfere with components of the immunological niche, leading to activation of anti-inflammatory pathways and inhibition of several mediators of inflammation. In summary, xenobiotics may reduce disease-related gut mucosal alterations and clinical symptoms. Studying the complex interplay between gut immunological niche and xenobiotics will certainly open new horizons in the knowledge and therapy of intestinal pathologies.

Intestinal helminth infection drives carcinogenesis in colitis-associated colon cancer

Inflammatory bowel diseases (IBD) are chronic inflammatory disorders of the gastrointestinal tract, strongly associated with an increased risk of colorectal cancer development. Parasitic infections caused by helminths have been shown to modulate the host’s immune response by releasing immunomodulatory molecules and inducing regulatory T cells (Tregs). This immunosuppressive state provoked in the host has been considered as a novel and promising approach to treat IBD patients and alleviate acute intestinal inflammation. On the contrary, specific parasite infections are well known to be directly linked to carcinogenesis. Whether a helminth infection interferes with the development of colitis-associated colon cancer (CAC) is not yet known. In the present study, we demonstrate that the treatment of mice with the intestinal helminth Heligmosomoides polygyrus at the onset of tumor progression in a mouse model of CAC does not alter tumor growth and distribution. In contrast, H. polygyrus infection in the early inflammatory phase of CAC strengthens the inflammatory response and significantly boosts tumor development. Here, H. polygyrus infection was accompanied by long-lasting alterations in the colonic immune cell compartment, with reduced frequencies of colonic CD8⁺ effector T cells. Moreover, H. polygyrus infection in the course of dextran sulfate sodium (DSS) mediated colitis significantly exacerbates intestinal inflammation by amplifying the release of colonic IL-6 and CXCL1. Thus, our findings indicate that the therapeutic application of helminths during CAC might have tumor-promoting effects and therefore should be well-considered.

Evidence from epidemiological studies indicates an inverse correlation between the incidence of certain immune-mediated diseases, including inflammatory bowel diseases, and exposure to helminths. As a consequence, helminth parasites were tested for treating IBD patients, resulting in clinical amelioration of the disease due to the induction of an immunosuppressive microenvironment. However, some infection–related cancers can be attributed to helminth infection, probably due to the generation of a microenvironment that might be conductive to the initiation and development of cancer. In the present study, we aimed to unravel the apparently controversial function of helminths in a mouse model of colitis-associated colon cancer. We show that helminth infection in the onset of colitis and colitis-associated colon cancer does not ameliorate colonic inflammation but activates intestinal immune cells that further facilitate tumor development. Therefore, a better understanding of mechanisms by which helminths modulate host immune responses in the gut should be defined precisely before application of helminths in autoimmune diseases like IBD.

Role of MiRNAs in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD), mainly including Crohn's disease and ulcerative colitis, are characterized by chronic inflammation of the gastrointestinal tract. Despite improvements in detection, drug treatment and surgery, the pathogenesis of IBD has not been clarified. A number of miRNAs have been found to be involved in the initiation, development and progression of IBD, and they may have the potential to be used as biomarkers and therapeutic targets. Here, we have summarized the recent advances about the roles of miRNAs in IBD and analyzed the contribution of miRNAs to general diagnosis, differential diagnosis and activity judgment of IBD. Furthermore, we have also elaborated the promising role of miRNAs in IBD-related cancer prevention and prognosis prediction.

Crosstalk between intestinal epithelial cell and adaptive immune cell in intestinal mucosal immunity

Constantly challenged by luminal bacteria, intestinal epithelium forms both a physical and biochemical defense against pathogens. Besides, intestinal epithelium senses dynamic and continuous changes in luminal environment and transmits signals to subjacent immune cells accordingly. It has been long accepted that adaptive immune cells fulfill their roles partly by modulating function of intestinal epithelial cells. Recent studies have brought up the proposal that intestinal epithelial cells also actively participate in the regulation of adaptive immunity, especially CD4+ adaptive T cells, which indicates that there is reciprocal crosstalk between intestinal epithelial cells and adaptive immune cells, and the crosstalk may play important role in intestinal mucosal immunity. This Review makes a comprehensive summary about crosstalk between intestinal epithelial cells and CD4+ adaptive T cells in intestinal immunity. Special attention would be given to their implications in inflammatory bowel disease pathogenesis and potential therapeutic targets.

Induction of Colonic Regulatory T Cells by Mesalamine by Activating the Aryl Hydrocarbon Receptor

BACKGROUND & AIMS

Mesalamine is a first-line drug for treatment of inflammatory bowel diseases (IBD). However, its mechanisms are not fully understood. CD4⁺ Foxp3⁺ regulatory T cells (Tregs) play a potential role in suppressing IBD. This study determined whether the anti-inflammatory activity of mesalamine is related to Treg induction in the colon.

METHODS

We examined the frequencies of Tregs in the colons of wild-type mice, mice deficient for aryl hydrocarbon receptor (AhR^-/- mice), and bone marrow-chimeric mice lacking AhR in hematopoietic cells (BM-AhR^-/- mice), following oral treatment with mesalamine. We also examined the effects of mesalamine on transforming growth factor (TGF)-β expression in the colon.

RESULTS

Treatment of wild-type mice with mesalamine increased the accumulation of Tregs in the colon and up-regulated the AhR target gene Cyp1A1, but this effect was not observed in AhR^-/- or BM-AhR^-/- mice. In addition, mesalamine promoted in vitro differentiation of naive T cells to Tregs, concomitant with AhR activation. Mice treated with mesalamine exhibited increased levels of the active form of TGF-β in the colon in an AhR-dependent manner and blockade of TGF-β signaling suppressed induction of Tregs by mesalamine in the colon. Furthermore, mice pretreated with mesalamine acquired resistance to dextran sodium sulfate-induced colitis.

CONCLUSIONS

We propose a novel anti-inflammatory mechanism of mesalamine for colitis: induction of Tregs in the colon via the AhR pathway, followed by TGF-β activation.

P2X7 receptor promotes intestinal inflammation in chemically induced colitis and triggers death of mucosal regulatory T cells

P2X7 receptor activation contributes to inflammation development in different pathologies. We previously reported that the P2X7 receptor is over-expressed in the gut mucosa of patients with inflammatory bowel disease, and that P2X7 inhibition protects against chemically induced colitis. Here, we investigated in detail the role of the P2X7 receptor in inflammatory bowel disease development, by treating P2X7 knockout (KO) and WT mice with two different (and established) colitis inductors. P2X7 KO mice were protected against gut inflammation induced by 2,4,6-trinitrobenzenesulfonic acid or oxazolone, with no weight loss or gut histological alterations after treatment. P2X7 receptor knockout induced regulatory T cell accumulation in the colon, as evaluated by qRT-PCR for FoxP3 expression and immunostaining for CD90/CD45RB^low. Flow cytometry analysis of mesenteric lymph node cells showed that P2X7 activation (by ATP) triggered regulatory T cell death. In addition, such cells from P2X7 KO mice expressed more CD103, suggesting increased migration of regulatory T cells to the colon (relative to the WT). Our results show that the P2X7 has a key role during inflammation development in inflammatory bowel disease, by triggering the death and retention in the mesenteric lymph nodes of regulatory T cells that would otherwise promote immune system tolerance in the gut.

Intestinal microbiota sustains inflammation and autoimmunity induced by hypomorphic RAG defects

Rigoni et al. report that hypomorphic Rag2^R229Q mutation is associated with altered microbiota composition and defects in the gut–blood barrier and suggest that intestinal microbes may play a critical role in the distinctive immune dysregulation of Omenn syndrome.

Omenn syndrome (OS) is caused by hypomorphic Rag mutations and characterized by a profound immunodeficiency associated with autoimmune-like manifestations. Both in humans and mice, OS is mediated by oligoclonal activated T and B cells. The role of microbial signals in disease pathogenesis is debated. Here, we show that Rag2^R229Q knock-in mice developed an inflammatory bowel disease affecting both the small bowel and colon. Lymphocytes were sufficient for disease induction, as intestinal CD4 T cells with a Th1/Th17 phenotype reproduced the pathological picture when transplanted into immunocompromised hosts. Moreover, oral tolerance was impaired in Rag2^R229Q mice, and transfer of wild-type (WT) regulatory T cells ameliorated bowel inflammation. Mucosal immunoglobulin A (IgA) deficiency in the gut resulted in enhanced absorption of microbial products and altered composition of commensal communities. The Rag2^R229Q microbiota further contributed to the immunopathology because its transplant into WT recipients promoted Th1/Th17 immune response. Consistently, long-term dosing of broad-spectrum antibiotics (ABXs) in Rag2^R229Q mice ameliorated intestinal and systemic autoimmunity by diminishing the frequency of mucosal and circulating gut-tropic CCR9⁺ Th1 and Th17 T cells. Remarkably, serum hyper-IgE, a hallmark of the disease, was also normalized by ABX treatment. These results indicate that intestinal microbes may play a critical role in the distinctive immune dysregulation of OS.