Small intestinal CD103+ dendritic cells display unique functional properties that are conserved between mice and humans

Ligands for Intestinal Intraepithelial T Lymphocytes in Health and Disease

The intestinal tract is constantly exposed to a diverse mixture of luminal antigens, such as those derived from commensals, dietary substances, and potential pathogens. It also serves as a primary route of entry for pathogens. At the forefront of this intestinal defense is a single layer of epithelial cells that forms a critical barrier between the gastrointestinal (GI) lumen and the underlying host tissue. The intestinal intraepithelial T lymphocytes (T-IELs), one of the most abundant lymphocyte populations in the body, play a crucial role in actively surveilling and maintaining the integrity of this barrier by tolerating non-harmful factors such as commensal microbiota and dietary components, promoting epithelial turnover and renewal while also defending against pathogens. This immune balance is maintained through interactions between ligands in the GI microenvironment and receptors on T-IELs. This review provides a detailed examination of the ligands present in the intestinal epithelia and the corresponding receptors expressed on T-IELs, including T cell receptors (TCRs) and non-TCRs, as well as how these ligand-receptor interactions influence T-IEL functions under both steady-state and pathological conditions. By understanding these engagements, we aim to shed light on the mechanisms that govern T-IEL activities within the GI microenvironment. This knowledge may help in developing strategies to target GI ligands and modulate T-IEL receptor expression, offering precise approaches for treating intestinal disorders.

Mouse Models Enable the Functional Investigation of Tertiary Lymphoid Structures in Cancer

Tertiary lymphoid structures (TLSs) are organized lymphoid aggregates that form within nonlymphoid tissue, including tumors, in response to persistent inflammatory stimulation. In cancer patients, TLSs are generally associated with positive clinical outcomes. However, the cellular composition and spatial distribution of TLSs can vary depending on the underlying disease state, complicating interpretations of their prognostic significance. Murine models are indispensable for providing a deeper insight into the mechanisms involved in TLS formation and function. Studies using these models can complement current clinical efforts to characterize TLSs via genetic sequencing and histopathology of human samples. Several features of TLSs resemble that of secondary lymphoid organs (SLOs). Consequently, vascular system components and structural support elements are important for TLS formation and maintenance. Furthermore, TLSs in different tissue environments can exhibit distinct characteristics, necessitating careful consideration when selecting mouse models for study. Herein, we discuss critical aspects to consider when modeling TLSs and describe recent findings of TLS studies in the mouse lung and intestinal gut environments as examples to highlight the importance of considering tissue-specific regulatory mechanisms for TLSs. In this chapter, we also summarize the mechanistic insights derived from murine models on the formation and function of TLSs, which may translate to the future therapeutic modulation of TLS in disease.

Combined TLR2/TLR4 activation equip non-mucosal dendritic cells to prime Th1 cells with gut tropism

Activated CD4+ T cells located at mucosal surfaces orchestrate local effector immune mechanisms. When properly polarized, these cells contribute to block infections at early stages and may be essential to restrain the local growth of mucosal tumors, playing a critical role in host protection. How CD4+ T cells simultaneously integrate gut-homing instructions and Th polarization signals transmitted by TLR activated dendritic cells (DCs) is unknown. Here, we show that the combined activation through TLR2, which alone does not induce a clear Th polarization, and TLR4, which alone does not imprint mucosal tropism, equip non-mucosal DCs to prime gut-homing CD4+ T cells with reinforced Th1 polarization. These results show that targeting DCs with combined innate stimuli with distinct properties is a rational strategy to program the outcome of T cell polarization and simultaneously control their tissue tropism. Exploring this strategy could enhance the efficacy of vaccines and immune cell therapies.

Intestinal Lymphatic Biology, Drug Delivery, and Therapeutics: Current Status and Future Directions

Historically, the intestinal lymphatics were considered passive conduits for fluids, immune cells, dietary lipids, lipid soluble vitamins, and lipophilic drugs. Studies of intestinal lymphatic drug delivery in the late 20th century focused primarily on the drugs' physicochemical properties, especially high lipophilicity, that resulted in intestinal lymphatic transport. More recent discoveries have changed our traditional view by demonstrating that the lymphatics are active, plastic, and tissue-specific players in a range of biological and pathological processes, including within the intestine. These findings have, in turn, inspired exploration of lymph-specific therapies for a range of diseases, as well as the development of more sophisticated strategies to actively deliver drugs or vaccines to the intestinal lymph, including a range of nanotechnologies, lipid prodrugs, and lipid-conjugated materials that "hitchhike" onto lymphatic transport pathways. With the increasing development of novel therapeutics such as biologics, there has been interest in whether these therapeutics are absorbed and transported through intestinal lymph after oral administration. Here we review the current state of understanding of the anatomy and physiology of the gastrointestinal lymphatic system in health and disease, with a focus on aspects relevant to drug delivery. We summarize the current state-of-the-art approaches to deliver drugs and quantify their uptake into the intestinal lymphatic system. Finally, and excitingly, we discuss recent examples of significant pharmacokinetic and therapeutic benefits achieved via intestinal lymphatic drug delivery. We also propose approaches to advance the development and clinical application of intestinal lymphatic delivery strategies in the future. SIGNIFICANCE STATEMENT: This comprehensive review details the understanding of the anatomy and physiology of the intestinal lymphatic system in health and disease, with a focus on aspects relevant to drug delivery. It highlights current state-of-the-art approaches to deliver drugs to the intestinal lymphatics and the shift toward the use of these strategies to achieve pharmacokinetic and therapeutic benefits for patients.

Microbiota activation and regulation of adaptive immunity

In the mucosa, T cells and B cells of the immune system are essential for maintaining immune homeostasis by suppressing reactions to harmless antigens and upholding the integrity of intestinal mucosal barrier functions. Host immunity and homeostasis are regulated by metabolites produced by the gut microbiota, which has developed through the long-term coevolution of the host and the gut biome. This is achieved by the immunological system's tolerance for symbiote microbiota, and its ability to generate a proinflammatory response against invasive organisms. The imbalance of the intestinal immune system with commensal organisms is causing a disturbance in the homeostasis of the gut microbiome. The lack of balance results in microbiota dysbiosis, the weakened integrity of the gut barrier, and the development of inflammatory immune reactions toward symbiotic organisms. Researchers may uncover potential therapeutic targets for preventing or regulating inflammatory diseases by understanding the interactions between adaptive immunity and the microbiota. This discussion will explore the connection between adaptive immunity and microbiota.

Efficacy and safety of etrolizumab in the treatment of inflammatory bowel disease: a meta-analysis

Background

To explore the efficacy and safety of etrolizumab in treating inflammatory bowel disease (IBD) through meta-analysis.

Method

A comprehensive exploration encompassed randomized controlled trials examining the efficacy of etrolizumab in treating IBD across PubMed, Embase, Cochrane library, and Web of Science, with a search deadline of 1 December 2023. Quality assessment leaned on the Cochrane manual's risk-of-bias evaluation, while Stata 15 undertook the data analysis.

Result

Five randomized controlled studies involving 1682 individuals were finally included, Meta-analysis results suggested that compared with placebo, etrolizumab could improve clinical response (RR = 1.26, 95% CI [1.04-1.51]), clinical remission (RR = 1.26, 95% CI [1.04-1.51]) in IBD patients. Endoscopic alleviate (RR = 2.10, 95% CI [1.56-2.82]), endoscopic improvement (RR = 2.10, 95% CI [1.56-2.82]), endoscopic remission (RR = 2.10, 95% CI [1.56-2.82]), Endoscopic improvement (RR = 1.56, 95% CI [1.30-1.89]), histological remission (RR = 1.62, 95% CI [1.26-2.08]), and did not increase any adverse events (RR = 0.95, 95% CI [0.90-1.01]) and serious adverse events (RR = 0.94, 95% CI [0.68-1.31]).

Conclusion

According to our current study, etrolizumab is a promising drug in IBD.

Exploring the Interplay between Fatty Acids, Inflammation, and Type 2 Diabetes

Around 285 million people worldwide currently have type 2 diabetes and it is projected that this number will be surpassed by 2030. Therefore, it is of the utmost importance to enhance our comprehension of the disease's development. The regulation of diet, obesity, and inflammation in type 2 diabetes is believed to play a crucial role in enhancing insulin sensitivity and reducing the risk of onset diabetes. Obesity leads to an increase in visceral adipose tissue, which is a prominent site of inflammation in type 2 diabetes. Dyslipidemia, on the other hand, plays a significant role in attracting activated immune cells such as macrophages, dendritic cells, T cells, NK cells, and B cells to visceral adipose tissue. These immune cells are a primary source of pro-inflammatory cytokines that are believed to promote insulin resistance. This review delves into the influence of elevated dietary free saturated fatty acids and examines the cellular and molecular factors associated with insulin resistance in the initiation of inflammation induced by obesity. Furthermore, it explores novel concepts related to diet-induced inflammation and its relationship with type 2 diabetes.

Microglia/macrophage-specific deletion of TLR-4 protects against neural effects of diet-induced obesity

Obesity is associated with numerous adverse neural effects, including reduced neurogenesis, cognitive impairment, and increased risks for developing Alzheimer's disease (AD) and vascular dementia. Obesity is also characterized by chronic, low-grade inflammation that is implicated in mediating negative consequences body-wide. Toll-like receptor 4 (TLR4) signaling from peripheral macrophages is implicated as an essential regulator of the systemic inflammatory effects of obesity. In the brain, obesity drives chronic neuroinflammation that involves microglial activation, however the contributions of microglia-derived TLR4 signaling to the consequences of obesity are poorly understood. To investigate this issue, we first generated mice that carry an inducible, microglia/macrophage-specific deletion of TLR4 that yields long-term TLR4 knockout only in brain indicating microglial specificity. Next, we analyzed the effects of microglial TLR4 deletion on systemic and neural effects of a 16-week of exposure to control versus obesogenic high-fat diets. In male mice, TLR4 deletion generally yielded limited effects on diet-induced systemic metabolic dysfunction but significantly reduced neuroinflammation and impairments in neurogenesis and cognitive performance. In female mice maintained on obesogenic diet, TLR4 deletion partially protected against weight gain, adiposity, and metabolic impairments. Compared to males, females showed milder diet-induced neural consequences, against which TLR4 deletion was protective. Collectively, these findings demonstrate a central role of microglial TLR4 signaling in mediating the neural effects of obesogenic diet and highlight sexual dimorphic responses to both diet and TLR4.

Targeting T-cell integrins in autoimmune and inflammatory diseases

The recruitment of T cells to tissues and their retention there are essential processes in the pathogenesis of many autoimmune and inflammatory diseases. The mechanisms regulating these processes have become better understood over the past three decades and are now recognized to involve temporally and spatially specific interactions between cell-adhesion molecules. These include integrins, which are heterodimeric molecules that mediate in-to-out and out-to-in signalling in T cells, other leukocytes, and most other cells of the body. Integrin signalling contributes to T-cell circulation through peripheral lymph nodes, immunological synapse stability and function, extravasation at the sites of inflammation, and T-cell retention at these sites. Greater understanding of the contribution of integrin signalling to the role of T cells in autoimmune and inflammatory diseases has focused much attention on the development of therapeutics that target T-cell integrins. This literature review describes the structure, activation, and function of integrins with respect to T cells, then discusses the use of integrin-targeting therapeutics in inflammatory bowel disease, multiple sclerosis, and psoriasis. Efficacy and safety data from clinical trials and post-marketing surveillance are presented for currently approved therapeutics, therapeutics that have been withdrawn from the market, and novel therapeutics currently in clinical trials. This literature review will inform the reader of the current means of targeting T-cell integrins in autoimmune and inflammatory diseases, as well as recent developments in the field.

Oral Administration of Cancer Vaccines: Challenges and Future Perspectives

Cancer vaccines, a burgeoning strategy in cancer treatment, are exploring innovative administration routes to enhance patient and medical staff experiences, as well as immunological outcomes. Among these, oral administration has surfaced as a particularly noteworthy approach, which is attributed to its capacity to ignite both humoral and cellular immune responses at systemic and mucosal tiers, thereby potentially bolstering vaccine efficacy comprehensively and durably. Notwithstanding this, the deployment of vaccines through the oral route in a clinical context is impeded by multifaceted challenges, predominantly stemming from the intricacy of orchestrating effective oral immunogenicity and necessitating strategic navigation through gastrointestinal barriers. Based on the immunogenicity of the gastrointestinal tract, this review critically analyses the challenges and recent advances and provides insights into the future development of oral cancer vaccines.

TGF-β1 signaling and Smad7 control T-cell responses in health and immune-mediated disorders

Transforming growth factor (TGF)-β1, a member of the TGF-β superfamily, is produced by many immune and nonimmune cells and has pleiotropic effects on both innate and adaptive immunity, especially in the control of T-cell differentiation and function. Consistently, loss of TGF-β1 function is associated with exacerbated T-cell-dependent inflammatory responses that culminate in pathological processes in allergic and immune-mediated diseases. In this review, we highlight the roles of TGF-β1 in immunity, focusing mainly on its ability to promote differentiation of regulatory T cells, T helper (Th)-17, and Th9 cells, thus contributing to amplifying or restricting T-cell responses in health and human diseases (e.g., inflammatory bowel diseases, type 1 diabetes, asthma, and MS). In addition, we discuss the involvement of Smad7, an inhibitor of TGF-β1 signaling, in immune-mediated disorders (e.g., psoriasis, rheumatoid arthritis, MS, and inflammatory bowel diseases), as well as the discordant results of clinical trials with mongersen, an oral pharmaceutical compound containing a Smad7 antisense oligonucleotide, in patients with Crohn's disease. Further work is needed to ascertain the reasons for such a discrepancy as well as to identify better candidates for treatment with Smad7 inhibitors.

A novel peanut allergy immunotherapy: Plant-based enveloped Ara h 2 Bioparticles activate dendritic cells and polarize T cell responses to Th1

Introduction

As the only market-authorized allergen immunotherapy (AIT) for peanut allergy is accompanied by a high risk of side effects and mainly induces robust desensitization without sustained efficacy, novel treatment options are required. Peanut-specific plant-derived eBioparticles (eBPs) surface expressing Ara h 2 at high density have been shown to be very hypoallergenic. Here, we assessed the dendritic cell (DC)-activating and T cell polarization capacity of these peanut-specific eBPs.

Methods

Route and kinetics of eBP uptake were studied by (imaging) flow cytometry using monocyte-derived DCs incubated with fluorescently-labelled Ara h 2 eBPs or natural Ara h 2 (nAra h 2) in the presence or absence of inhibitors that block pathways involved in macropinocytosis, phagocytosis, and/or receptor-mediated uptake. DC activation was monitored by flow cytometry (maturation marker expression) and ELISA (cytokine production). T cell polarization was assessed by co-culturing DCs exposed to Ara h 2 eBPs or nAra h 2 with naïve CD4+ T cells, followed by flow cytometry assessment of intracellular IFNγ+ (Th1) and IL-13+ (Th2), and CD25+CD127-Foxp3+ regulatory T cells (Tregs). The suppressive activity of Tregs was tested using a suppressor assay.

Results

Ara h 2 eBPs were taken up by DCs through actin-dependent pathways. They activated DCs demonstrated by an induced expression of CD83 and CD86, and production of TNFα, IL-6, and IL-10. eBP-treated DCs polarized naïve CD4+ T cells towards Th1 cells, while reducing Th2 cell development. Furthermore, eBP-treated DCs induced reduced the frequency of Foxp3+ Tregs but did not significantly affect T cell IL-10 production or T cells with suppressive capacity. In contrast, DC activation and Th1 cell polarization were not observed for nAra h 2.

Conclusion

Ara h 2 eBPs activate DCs that subsequently promote Th1 cell polarization and reduce Th2 cell polarization. These characteristics mark Ara h 2 eBPs as a promising novel candidate for peanut AIT.

Next Generation Mucosal Vaccine Strategy for Respiratory Pathogens

Inducing humoral and cytotoxic mucosal immunity at the sites of pathogen entry has the potential to prevent the infection from getting established. This is different from systemic vaccination, which protects against the development of systemic symptoms. The field of mucosal vaccination has seen fewer technological advances compared to nucleic acid and subunit vaccine advances for injectable vaccine platforms. The advent of the next-generation adenoviral vectors has given a boost to mucosal vaccine research. Basic research into the mechanisms regulating innate and adaptive mucosal immunity and the discovery of effective and safe mucosal vaccine adjuvants will continue to improve mucosal vaccine design. The results from clinical trials of inhaled COVID-19 vaccines demonstrate their ability to induce the proliferation of cytotoxic T cells and the production of secreted IgA and IgG antibodies locally, unlike intramuscular vaccinations. However, these mucosal vaccines induce systemic immune responses at par with systemic vaccinations. This review summarizes the function of the respiratory mucosa-associated lymphoid tissue and the advantages that the adenoviral vectors provide as inhaled vaccine platforms.

The food additive titanium dioxide hinders intestinal production of TGF-β and IL-10 in mice, and long-term exposure in adults or from perinatal life blocks oral tolerance to ovalbumin

Food hypersensitivities are increasing in industrialized countries, and foodborne nanoparticles (NPs) are suspected as co-factors in their aetiology. Food-grade titanium dioxide (fg-TiO2), a food colouring agent, is composed of NPs with immunomodulatory properties. We investigated whether fg-TiO2 may compromise the establishment of oral tolerance (OT) to food proteins using a model of OT induction to ovalbumin (OVA) in mice, and whether a perinatal exposure could trigger this effect. In pregnant mice fed a TiO2-enriched diet, ICP-MS and TEM-EDX analyses showed passage of TiO2 NPs into the foetus. When their weaned offspring were fed the same diet, a breakdown in OT to OVA was observed at adulthood, characterized by a high anti-OVA IgG production compared to controls. However, adult mice directly exposed to fg-TiO2 did not induce OT to OVA either, ruling out a developmental origin for these effects. When these mice were orally challenged with OVA, intestinal inflammation demonstrated hypersensitivity to OVA. In OVA-naïve mice, fg-TiO2 exposure impaired intestinal TGF-β and IL-10 production, of key role in OT induction and maintenance. These findings showed that long-term exposure to TiO2 as food additive alters anti-inflammatory cytokine profile, and leads to OT failure regardless of the timing of TiO2 exposure throughout life.

The intestinal immune system and gut barrier function in obesity and ageing

Obesity and ageing predispose to numerous, yet overlapping chronic diseases. For example, metabolic abnormalities, including insulin resistance (IR) and type 2 diabetes (T2D) are important causes of morbidity and mortality. Low-grade chronic inflammation of tissues, such as the liver, visceral adipose tissue and neurological tissues, is considered a significant contributor to these chronic diseases. Thus, it is becoming increasingly important to understand what drives this inflammation in affected tissues. Recent evidence, especially in the context of obesity, suggests that the intestine plays an important role as the gatekeeper of inflammatory stimuli that ultimately fuels low-grade chronic tissue inflammation. In addition to metabolic diseases, abnormalities in the intestinal mucosal barrier have been linked to a range of other chronic inflammatory conditions, such as neurodegeneration and ageing. The flow of inflammatory stimuli from the gut is in part controlled by local immunological inputs impacting the intestinal barrier. Here, we will review the impact of obesity and ageing on the intestinal immune system and its downstream consequences on gut barrier function, which is strongly implicated in the pathogenesis of obesity and age-related diseases. In particular, we will discuss the effects of age-related intestinal dysfunction on neurodegenerative diseases.

The Underappreciated Role of Secretory IgA in IBD

Eighty percent of antibody secreting cells (ASCs) are found in the intestine, where they produce grams of immunoglobulin (Ig) A daily. immunoglobulin A is actively transcytosed into the lumen, where it plays a critical role in modulating the gut microbiota. Although loss of immune tolerance to bacterial antigens is the likely trigger of the dysregulated immune response that characterizes inflammatory bowel disease (IBD), little effort has been placed on understanding the interface between B cells, IgA, and the microbiota during initiation or progression of disease. This may be in part due to the misleading fact that IgA-deficient humans are mostly asymptomatic, likely due to redundant role of secretory (S) IgM. Intestinal B cell recruitment is critically dependent on integrin α4β7-MAdCAM-1 interactions, yet antibodies that target α4β7 (ie, vedolizumab), MAdCAM-1 (ie, ontamalimab), or both β7 integrins (α4β7 and αE [CD103] β7; etrolizumab) are in clinical use or development as IBD therapeutics. The effect of such interventions on the biology of IgA is largely unknown, yet a single dose of vedolizumab lowers SIgA levels in stool and weakens the oral immunization response to cholera vaccine in healthy volunteers. Thus, it is critical to further understand the role of these integrins for the migration of ASC and other cellular subsets during homeostasis and IBD-associated inflammation and the mode of action of drugs that interfere with this traffic. We have recently identified a subset of mature ASC that employs integrin αEβ7 to dock with intestinal epithelial cells, predominantly in the pericryptal region of the terminal ileum. This role for the integrin had not been appreciated previously, nor the αEβ7-dependent mechanism of IgA transcytosis that it supports. Furthermore, we find that B cells more than T cells are critically dependent on α4β7-MAdCAM-1 interactions; thus MAdCAM-1 blockade and integrin-β7 deficiency counterintuitively hasten colitis in interleukin-10-deficient mice. In both cases, de novo recruitment of IgA ASC to the intestinal lamina propria is compromised, leading to bacterial overgrowth, dysbiosis, and lethal colitis. Thus, despite the safe and effective use of anti-integrin antibodies in patients with IBD, much remains to be learned about their various cell targets.

Immune regulation through tryptophan metabolism

Amino acids are fundamental units of molecular components that are essential for sustaining life; however, their metabolism is closely interconnected to the control systems of cell function. Tryptophan (Trp) is an essential amino acid catabolized by complex metabolic pathways. Several of the resulting Trp metabolites are bioactive and play central roles in physiology and pathophysiology. Additionally, various physiological functions of Trp metabolites are mutually regulated by the gut microbiota and intestine to coordinately maintain intestinal homeostasis and symbiosis under steady state conditions and during the immune response to pathogens and xenotoxins. Cancer and inflammatory diseases are associated with dysbiosis- and host-related aberrant Trp metabolism and inactivation of the aryl hydrocarbon receptor (AHR), which is a receptor of several Trp metabolites. In this review, we focus on the mechanisms through which Trp metabolism converges to AHR activation for the modulation of immune function and restoration of tissue homeostasis and how these processes can be targeted using therapeutic approaches for cancer and inflammatory and autoimmune diseases.

Non-mucosal vaccination strategies to enhance mucosal immunity

The SARS-CoV-2 pandemic has highlighted the need for improved vaccines that can elicit long-lasting mucosal immunity. Although mucosal delivery of vaccines represents a plausible method to enhance mucosal immunity, recent studies utilizing intradermal vaccine delivery or incorporation of unique adjuvants suggest that mucosal immunity may be achieved by vaccination via non-mucosal routes. In this expert insight, we highlight emerging evidence from pre-clinical studies that warrant further mechanistic investigation to improve next-generation vaccines against mucosal pathogens, especially those with pandemic potential.

Specific and nonspecific nutritional interventions enhance the development of oral tolerance in food allergy

The goal of food allergy (FA) prevention and treatment is to induce oral tolerance (OT). Appropriate nutritional interventions are essential to induce OT to food allergens. This review introduces the mechanism of OT and the importance of early nutritional interventions, and then firstly summarizes specific nutritional factors to induce the development of OT of FA, including proteins, vitamins, fatty acids, saccharides and probiotics. The regulatory mechanism mainly induces the development of tolerance by increasing local or systemic protective regulatory T cells (Tregs) to suppress FA, while the gut microbiota may also be changed to maintain intestinal homeostasis. For allergens-specific OT, the disruption to the structure of proteins and epitopes is critical for the induction of tolerance by hydrolyzed and heated proteins. Vitamins (vitamin A, D), fatty acids, saccharides and probiotics as allergens nonspecific OT also induce the development of OT through immunomodulatory effects. This review contributes to our understanding of OT in FA through nutritional interventions. Nutritional interventions play an important role in the induction of OT, and offer promising approaches to reduce allergy risk and alleviate FA. Moreover, due to the importance and diversity of nutrition, it must be the future trend of induction of OT in FA.

Reduction of donor mononuclear phagocytes with clodronate-liposome during ex vivo lung perfusion attenuates ischemia-reperfusion injury

OBJECTIVES

Clodronate-liposome is used for depleting mononuclear phagocytes associated with ischemia-reperfusion injury. We hypothesized that administration of clodronate-liposome into the perfusate during ex vivo lung perfusion could reduce mononuclear phagocytes and attenuate ischemia-reperfusion injury.

METHODS

First, the number of mononuclear phagocytes in flushed grafts (minimum cold ischemic time, 6-hour cold ischemic time, 15-hour cold ischemic time, and 18-hour cold ischemic time; n = 6 each) was determined using flow cytometry. Second, grafts (15-hour cold ischemic time) were allocated to control or clodronate (n = 5 each). In the clodronate group, clodronate-liposome is administered into the perfusate. After 4 hours of ex vivo lung perfusion, the number of mononuclear phagocytes in the perfusate and lung tissues was measured. Third, grafts (15-hour cold ischemic time) were allocated to control or clodronate (n = 6 each). After 4 hours of ex vivo lung perfusion, the left lungs were transplanted and reperfused for 2 hours. Lung function was evaluated, and samples were analyzed.

RESULTS

First, mononuclear phagocytes remain in flushed grafts after prolonged cold ischemia. Second, the number of mononuclear phagocytes in lung tissues after ex vivo lung perfusion was significantly reduced in the clodronate group (P = .008). Third, lung compliance and vascular resistance during ex vivo lung perfusion were significantly improved in the clodronate group (P < .001 for both). Blood oxygenation and pulmonary edema were significantly improved in the clodronate group after 2 hours of reperfusion (P = .015 and P = .026, respectively). Histological findings showed reduced lung injury in the clodronate group (P = .013).

CONCLUSIONS

Administration of clodronate-liposome into the perfusate during ex vivo lung perfusion resulted in a significant reduction of mononuclear phagocytes in donor lungs, leading to attenuation of ischemia-reperfusion injury.

Smad7 as a positive regulator of intestinal inflammatory diseases

In physiological conditions, the human gut contains more immune cells than the rest of the body, but no overt tissue damage occurs, because several regulatory mechanisms control the activity of such cells thus preventing excessive and detrimental responses. One such mechanism relies on the action of transforming growth factor (TGF)-β1, a cytokine that targets both epithelial cells and many immune cell types. Loss of TGF-β1 function leads to intestinal pathology in both mice and humans. For instance, disruption of TGF-β1 signaling characterizes the destructive immune-inflammatory response in patients with Crohn's disease and patients with ulcerative colitis, the major human inflammatory bowel disease (IBD) entities. In these pathologies, the defective TGF-β1-mediated anti-inflammatory response is associated with elevated intestinal levels of Smad7, an antagonist of TGF-β1 signaling. Consistently, knockdown of Smad7 restores TGF-β1 function thereby attenuating intestinal inflammation in patients with IBD as well as in mice with IBD-like colitis. Up-regulation of Smad7 and reduced TGF-β1 signaling occurs also in necrotizing enterocolitis, environmental enteropathy, refractory celiac disease, and cytomegalovirus-induced colitis. In this article, we review the available data supporting the pathogenic role of Smad7 in the gastrointestinal tract and discuss whether and how targeting Smad7 can help attenuate detrimental immuno-inflammatory responses in the gut.

Contribution of Lactobacilli on Intestinal Mucosal Barrier and Diseases: Perspectives and Challenges of Lactobacillus casei

The intestine barrier, the front line of normal body defense, relies on its structural integrity, microbial composition and barrier immunity. The intestinal mucosal surface is continuously exposed to a complex and dynamic community of microorganisms. Although it occupies a relatively small proportion of the intestinal microbiota, Lactobacilli has been discovered to have a significant impact on the intestine tract in previous studies. It is undeniable that some Lactobacillus strains present probiotic properties through maintaining the micro-ecological balance via different mechanisms, such as mucosal barrier function and barrier immunity, to prevent infection and even to solve some neurology issues by microbiota-gut-brain/liver/lung axis communication. Notably, not only living cells but also Lactobacillus derivatives (postbiotics: soluble secreted products and para-probiotics: cell structural components) may exert antipathogenic effects and beneficial functions for the gut mucosal barrier. However, substantial research on specific effects, safety and action mechanisms in vivo should be done. In clinical application of humans and animals, there are still doubts about the precise evaluation of Lactobacilli's safety, therapeutic effect, dosage and other aspects. Therefore, we provide an overview of central issues on the impacts of Lactobacillus casei (L. casei) and their products on the intestinal mucosal barrier and some diseases and highlight the urgent need for further studies.

Long-term atorvastatin improves cognitive decline by regulating gut function in naturally ageing rats

Background

Statins have been widely used to prevent cardiovascular disease in middle-aged and elderly populations; however, the effect of long-term treatment on cognitive function is controversial. To simulate clinical conditions, middle-aged rats were given atorvastatin for 9 consecutive months to investigate the effect on natural cognitive decline and the possible mechanisms.

Results

The results showed that compared with the control group, long-term atorvastatin treatment naturally improved cognitive decline. Furthermore, long-term treatment regulated intestinal retinoic acid (RA) metabolism and storage by altering retinol dehydrogenase 7 (Rdh7) expression in the intestine, while RA metabolism affected the proliferation of intestinal Treg cells and inhibited IL-17+γδ T-cell function. In addition, long-term atorvastatin increased intestinal flora richness and decreased IL-17 expression in hippocampal tissue.

Conclusion

Collectively, these findings provide the first evidence that long-term atorvastatin intervention may prevent cognitive decline in naturally ageing rats by inhibiting neuroinflammation via the gut-brain axis.

Retinoid metabolism: new insights

Vitamin A (retinol) is a critical micronutrient required for the control of stem cell functions, cell differentiation, and cell metabolism in many different cell types, both during embryogenesis and in the adult organism. However, we must obtain vitamin A from food sources. Thus, the uptake and metabolism of vitamin A by intestinal epithelial cells, the storage of vitamin A in the liver, and the metabolism of vitamin A in target cells to more biologically active metabolites, such as retinoic acid (RA) and 4-oxo-RA, must be precisely regulated. Here, I will discuss the enzymes that metabolize vitamin A to RA and the cytochrome P450 Cyp26 family of enzymes that further oxidize RA. Because much progress has been made in understanding the regulation of ALDH1a2 (RALDH2) actions in the intestine, one focus of this review is on the metabolism of vitamin A in intestinal epithelial cells and dendritic cells. Another focus is on recent data that 4-oxo-RA is a ligand required for the maintenance of hematopoietic stem cell dormancy and the important role of RARβ (RARB) in these stem cells. Despite this progress, many questions remain in this research area, which links vitamin A metabolism to nutrition, immune functions, developmental biology, and nuclear receptor pharmacology.

(Not) Home alone: Antigen presenting cell - T Cell communication in barrier tissues

Priming of T cells by antigen presenting cells (APCs) is essential for T cell fate decisions, enabling T cells to migrate to specific tissues to exert their effector functions. Previously, these interactions were mainly explored using blood-derived cells or animal models. With great advances in single cell RNA-sequencing techniques enabling analysis of tissue-derived cells, it has become clear that subsets of APCs are responsible for priming and modulating heterogeneous T cell effector responses in different tissues. This composition of APCs and T cells in tissues is essential for maintaining homeostasis and is known to be skewed in infection and inflammation, leading to pathological T cell responses. This review highlights the commonalities and differences of T cell priming and subsequent effector function in multiple barrier tissues such as the skin, intestine and female reproductive tract. Further, we provide an overview of how this process is altered during tissue-specific infections which are known to cause chronic inflammation and how this knowledge could be harnessed to modify T cell responses in barrier tissue.

The unfulfilled potential of mucosal immunization

Recent events involving the global coronavirus pandemic have focused attention on vaccination strategies. Although tremendous advances have been made in subcutaneous and intramuscular vaccines during this time, one area that has lagged in implementation is mucosal immunization. Mucosal immunization provides several potential advantages over subcutaneous and intramuscular routes, including protection from localized infection at the site of entry, clearance of organisms on mucosal surfaces, induction of long-term immunity through establishment of central and tissue-resident memory cells, and the ability to shape regulatory responses. Despite these advantages, significant barriers remain to achieving effective mucosal immunization. The epithelium itself provides many obstacles to immunization, and the activation of immune recognition and effector pathways that leads to mucosal immunity has been difficult to achieve. This review will highlight the potential advantages of mucosal immunity, define the barriers to mucosal immunization, examine the immune mechanisms that need to be activated on mucosal surfaces, and finally address recent developments in methods for mucosal vaccination that have shown promise in generating immunity on mucosal surfaces in human trials.

Intestinal Uptake and Tolerance to Food Antigens

Food allergy is a growing concern due to its increasing world-wide incidence. Strict avoidance of allergens is a passive treatment strategy. Since the mechanisms responsible for the occurrence and development of food allergy have not yet been fully elucidated, effective individualized treatment options are lacking. In this review, we summarize the pathways through which food antigens enter the intestine and review the proposed mechanisms describing how the intestine acquires and tolerates food antigens. When oral tolerance is not established, food allergy occurs. In addition, we also discuss the contribution of commensal bacteria of the gut in shaping tolerance to food antigens in the intestinal tract. Finally, we propose that elucidating the mechanisms of intestinal uptake and tolerance of food antigens will provide additional clues for potential treatment options for food allergy.

Preparation and identification of monoclonal antibodies against porcine CD103

Dendritic cells (DCs) play an important role in activating, regulating, and maintaining the immune response. CD103+ DCs, one of the DC subpopulations, mainly function in the mucosal immune response. They are responsible for capturing and carrying antigens to the relevant lymph nodes to activate the downstream immune responses. However, there is limited available information regarding the function of CD103+ DCs in the porcine mucosal immune response. In this study, two monoclonal antibodies (mAbs) against porcine CD103 were prepared, and their applications were evaluated by enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence assay (IFA), and flow cytometry. The produced mAbs (7F3 and 9H3) were both IgG1 subtype with κ chains in the light chain. The 7F3 recognizes a linear epitope (PDLRPRAQVYFSDLE) while 9H3 recognizes another linear epitope (QILDEGQVLLGAVGA). The prepared mAbs could be used in vivo to detect the cells expressing CD103 molecules, giving wide applications of both mAbs. In conclusion, this study successfully prepared 2 mAbs against CD103 protein, and they showed applicability in vivo experiments, which will provide the basis for the study of porcine mucosal immunity. KEY POINTS: • Preparation of monoclonal antibodies against porcine CD103 molecule • Analysis of the distribution of CD103 protein on different cells is possible • Exploration of the CD103⁺ DCs function in porcine mucosal immunity is possible.

The role of retinoic acid in the production of immunoglobulin A

Vitamin A and its derivative retinoic acid (RA) play important roles in the regulation of mucosal immunity. The effect of vitamin A metabolism on T lymphocyte immunity has been well documented, but its role in mucosal B lymphocyte regulation is less well described. Intestinal immunoglobulin A (IgA) is key in orchestrating a balanced gut microbiota composition. Here, we describe the contribution of RA to IgA class switching in tissues including the lamina propria, mesenteric lymph nodes, Peyer's patches and isolated lymphoid follicles. RA can either indirectly skew T cells or directly affect B cell differentiation. IgA levels in healthy individuals are under the control of the metabolism of vitamin A, providing a steady supply of RA. However, IgA levels are altered in inflammatory bowel disease patients, making control of the metabolism of vitamin A a potential therapeutic target. Thus, dietary vitamin A is a key player in regulating IgA production within the intestine, acting via multiple immunological pathways.

Setd2 determines distinct properties of intestinal ILC3 subsets to regulate intestinal immunity

Subsets of group 3 innate lymphoid cells (ILC3s) are heterogeneous in development and function and play differential roles in intestinal immunity. Histone modifications are involved in the fate commitment of immune cells, including ILC3s. Here, we report that deletion of Setd2, histone H3K36 methyltransferase, in ILC3s results in increased generation of NKp46⁺ILC3s with enhanced cytotoxic signatures and tumor-suppressive capacity. Meanwhile, Rag1^-/-Rorc^CreSetd2^flox/flox mice have fewer CCR6⁺ILC3s and less defective solitary intestinal lymphoid tissue formation, accompanied by reduced granulocyte-macrophage colony-stimulating factor (GM-CSF) production by NKp46^-ILC3s and decreased CD11b⁺CD103⁺ dendritic cell accumulation. The deficiency of Setd2^-/-NKp46^-ILC3s may contribute to disturbed RORγt⁺Treg homeostasis and intestinal inflammation in Rag1^-/-Rorc^CreSetd2^flox/flox mice upon T cell reconstitution. Setd2 regulates genome accessibility imprinting gene mRNA expression, with a more profound effect on NKp46⁺ILC3s than NKp46^-ILC3s. Therefore, Setd2 determines distinct chromatin status and transcriptomic programs of ILC3 subsets to affect their function and intestinal immunity.

The Role of the Lymphatic System in the Pathogenesis and Treatment of Inflammatory Bowel Disease

Although the number of therapeutic options for the treatment of inflammatory bowel disease (IBD) has increased in recent years, patients suffer from decreased quality of life due to non-response or loss of response to the currently available treatments. An increased understanding of the disease’s etiology could provide novel insights for treatment strategies in IBD. Lymphatic system components are generally linked to immune responses and presumably related to inflammatory diseases pathophysiology. This review aims to summarize findings on immune-mediated mechanisms in lymphoid tissues linked with IBD pathogenesis and (potential) novel treatments. Enhanced innate and adaptive immune responses were observed in mesenteric lymph nodes (MLNs) and other lymphoid structures, such as Peyer’s patches, in patients with IBD and in animal models. Furthermore, the phenomenon of lymphatic obstruction in the form of granulomas in MLNs and lymphatic vessels correlates with disease activity. There is also evidence that abnormalities in the lymphatic stromal components and lymph node microbiome are common in IBD and could be exploited therapeutically. Finally, novel agents targeting lymphocyte trafficking have been added to the treatment armamentarium in the field of IBD. Overall, gut-associated lymphoid tissue plays a key role in IBD immunopathogenesis, which could offer novel therapeutic targets.

Intestinal Epithelial Cell Exosome Launches IL-1β-Mediated Neuron Injury in Sepsis-Associated Encephalopathy

Background

Gut–microbiota–brain axis links the relationship between intestinal microbiota and sepsis-associated encephalopathy (SAE). However, the key mediators between them remain unclear.

Methods

Memory test was determined by Water maze. Intestinal flora was measured by 16S RNA sequencing. Neurotransmitter was detected by high-performance liquid chromatography (HPLC). Histopathology was determined by H&E, immunofluorescence (IF), and terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) staining. Flow cytometry was employed to determine the proportion of macrophages.

Results

Fecal microbiota transplantation (FMT) relieved hippocampus impairment of SAE rats by inhibiting inflammation cytokine secretion, the expression of IBA-1 and neurotransmitter disturbance, and cell apoptosis and autophagy, accompanied by the reduced M1 polarization and M1 pro-inflammation factors produced by macrophages in mesenteric lymph nodes (MLNs). Actually, M1 polarization in SAE rats depended on intestinal epithelial cell (IEC)-derived exosome. GW4869-initiated inhibition of exosome secretion notably abolished M1 polarization and the secretion of IL-1β. However, GW4869-mediated improvement of hippocampus impairment was counteracted by the delivery of recombinant interleukin (IL)-1β to hippocampus. Mechanistically, IEC-derived exosome induced the excessive circulating IL-1β produced by CP-R048 macrophages, which subsequently induced damage and apoptosis of hippocampal neurons H19-7 in an autophagy-dependent manner. And reactivation of autophagy facilitates intestinal IL-1β-mediated hippocampal neuron injury.

Conclusion

Collectively, intestinal flora disturbance induced the exosome release of IECs, which subsequently caused M1 polarization in MLNs and the accumulation of circulating IL-1β. Circulating IL-1β promoted the damage and apoptosis of neurons in an autophagy-dependent manner. Possibly, targeting intestinal flora or IEC-derived exosome contributes to the treatment of SAE.

Change of Dendritic Cell Subsets Involved in Protection Against Listeria monocytogenes Infection in Short-Term-Fasted Mice

The gastrointestinal tract is the first organ directly affected by fasting. However, little is known about how fasting influences the intestinal immune system. Intestinal dendritic cells (DCs) capture antigens, migrate to secondary lymphoid organs, and provoke adaptive immune responses. We evaluated the changes of intestinal DCs in mice with short-term fasting and their effects on protective immunity against Listeria monocytogenes (LM). Fasting induced an increased number of CD103⁺CD11b⁻ DCs in both small intestinal lamina propria (SILP) and mesenteric lymph nodes (mLN). The SILP CD103⁺CD11b⁻ DCs showed proliferation and migration, coincident with increased levels of GM-CSF and C-C chemokine receptor type 7, respectively. At 24 h post-infection with LM, there was a significant reduction in the bacterial burden in the spleen, liver, and mLN of the short-term-fasted mice compared to those fed ad libitum. Also, short-term-fasted mice showed increased survival after LM infection compared with ad libitum-fed mice. It could be that significantly high TGF-β2 and Aldh1a2 expression in CD103⁺CD11b⁻ DCs in mice infected with LM might affect to increase of Foxp3⁺ regulatory T cells. Changes of major subset of DCs from CD103⁺ to CD103⁻ may induce the increase of IFN-γ–producing cells with forming Th1-biased environment. Therefore, the short-term fasting affects protection against LM infection by changing major subset of intestinal DCs from tolerogenic to Th1 immunogenic.

Dendritic cell functions in the inductive and effector sites of intestinal immunity

The intestine is constantly exposed to foreign antigens, which are mostly innocuous but can sometimes be harmful. Therefore, the intestinal immune system has the delicate task of maintaining immune tolerance to harmless food antigens while inducing tailored immune responses to pathogens and regulating but tolerating the microbiota. Intestinal dendritic cells (DCs) play a central role in these functions as sentinel cells able to prime and polarize the T cell responses. DCs are deployed throughout the intestinal mucosa but with local specializations along the gut length and between the diffuse effector sites of the gut lamina propria (LP) and the well-organized immune inductive sites comprising isolated lymphoid follicles (ILFs), Peyer's patches (PPs), and other species-specific gut-associated lymphoid tissues (GALTs). Understanding the specificities of each intestinal DC subset, how environmental factors influence DC functions, and how these can be modulated is key to harnessing the therapeutic potential of mucosal adaptive immune responses, whether by enhancing the efficacy of mucosal vaccines or by increasing tolerogenic responses in inflammatory disorders. In this review, we summarize recent findings related to intestinal DCs in steady state and upon inflammation, with a special focus on their functional specializations, highly dependent on their microenvironment.

Antibody secreting cells are critically dependent on integrin α4β7/MAdCAM-1 for intestinal recruitment and control of the microbiota during chronic colitis

T and B cells employ integrin α4β7 to migrate to intestine under homeostatic conditions. Whether those cells differentially rely on α4β7 for homing during inflammatory conditions has not been fully examined. This may have implications for our understanding of the mode of action of anti-integrin therapies in inflammatory bowel disease (IBD). Here, we examined the role of α4β7 integrin during chronic colitis using IL-10^-/- mice, β7-deficient IL-10^-/-, IgA-deficient IL-10^-/- mice, and antibody blockade of MAdCAM-1. We found that α4β7 was predominantly expressed by B cells. β7 deficiency and MAdCAM-1 blockade specifically depleted antibody secreting cells (ASC) (not T cells) from the colonic LP, leading to a fecal pan-immunoglobulin deficit, severe colitis, and alterations of microbiota composition. Colitis was not due to defective regulation, as dendritic cells (DC), regulatory T cells, retinaldehyde dehydrogenase (RALDH) expression, activity, and regulatory T/B-cell cytokines were all comparable between the strains/treatment. Finally, an IgA deficit closely recapitulated the clinical phenotype and altered microbiota composition of β7-deficient IL-10^-/- mice. Thus, a luminal IgA deficit contributes to accelerated colitis in the β7-deficient state. Given the critical/nonredundant dependence of IgA ASC on α4β7:MAdCAM-1 for intestinal homing, B cells may represent unappreciated targets of anti-integrin therapies.

Integrin αE(CD103)β7 in Epithelial Cancer

Interactions of both the innate and the adaptive immune system with tumors are complex and often influence courses and therapeutic treatments in unanticipated ways. Based on the concept that CD8+T cells can mediate important antitumor effects, several therapies now aim to amplify their specific activity. A subpopulation of CD8+ tissue-resident T lymphocytes that express the αE(CD103)β7 integrin has raised particular interest. This receptor presumably contributes to the recruitment and retention of tumor-infiltrating immune cells through interaction with its ligand, E-cadherin. It appears to have regulatory functions and is thought to be a component of some immunological synapses. In TGF-rich environments, the αE(CD103)β7/E-cadherin-interaction enhances the binding strength between tumor cells and infiltrating T lymphocytes. This activity facilitates the release of lytic granule contents and cytokines as well as further immune responses and the killing of target cells. Expression of αE(CD103)β7 in some tumors is associated with a rather favorable prognosis, perhaps with the notable exception of squamous cell carcinoma of the skin. Although epithelial skin tumors are by far the most common tumors of fair-skinned people, there have been very few studies on the distribution of αE(CD103)β7 expressing cells in these neoplasms. Given this background, we describe here that αE(CD103)β7 is scarcely present in basal cell carcinomas, but much more abundant in squamous cell carcinomas with heterogeneous distribution. Notwithstanding a substantial number of studies, the role of αE(CD103)β7 in the tumor context is still far from clear. Here, we summarize the essential current knowledge on αE(CD103)β7 and outline that it is worthwhile to further explore this intriguing receptor with regard to the pathophysiology, therapy, and prognosis of solid tumors.

Potential of human helminth therapy for resolution of inflammatory bowel disease: The future ahead

Inflammatory bowel disease (IBD) is associated with a dysregulated mucosal immune response in the gastrointestinal tract. The number of patients with IBD has increased worldwide, especially in highly industrialized western societies. The population of patients with IBD in North America is forecasted to reach about four million by 2030; meanwhile, there is no definitive therapy for IBD. Current anti-inflammatory, immunosuppressive, or biological treatment may induce and maintain remission, but not all patients respond to these treatments. Recent studies explored parasitic helminths as a novel modality of therapy due to their potent immunoregulatory properties in humans. Research using IBD animal models infected with a helminth or administered helminth-derived products such as excretory-secretory products has been promising, and helminth-microbiota interactions exert their anti-inflammatory effects by modulating the host immunity. Recent studies also indicate that evidence that helminth-derived metabolites may play a role in anticolitic effects. Thus, the helminth shows a potential benefit for treatment against IBD. Here we review the current feasibility of "helminth therapy" from the laboratory for application in IBD management.

The Role of the Immune System in IBD-Associated Colorectal Cancer: From Pro to Anti-Tumorigenic Mechanisms

Patients with inflammatory bowel disease (IBD) have increased incidence of colorectal cancer (CRC). IBD-associated cancer follows a well-characterized sequence of intestinal epithelial changes, in which genetic mutations and molecular aberrations play a key role. IBD-associated cancer develops against a background of chronic inflammation and pro-inflammatory immune cells, and their products contribute to cancer development and progression. In recent years, the effect of the immunosuppressive microenvironment in cancer development and progression has gained more attention, mainly because of the unprecedented anti-tumor effects of immune checkpoint inhibitors in selected groups of patients. Even though IBD-associated cancer develops in the background of chronic inflammation which is associated with activation of endogenous anti-inflammatory or suppressive mechanisms, the potential role of an immunosuppressive microenvironment in these cancers is largely unknown. In this review, we outline the role of the immune system in promoting cancer development in chronic inflammatory diseases such as IBD, with a specific focus on the anti-inflammatory mechanisms and suppressive immune cells that may play a role in IBD-associated tumorigenesis.

Intestinal mucus barrier: a missing piece of the puzzle in food allergy

The prevalence of food allergies has reached epidemic levels but the cause remains largely unknown. We discuss the clinical relevance of the gut mucosal barrier as a site for allergic sensitization to food. In this context, we focus on an important but overlooked part of the mucosal barrier in pathogenesis, the glycoprotein-rich mucus layer, and call attention to both beneficial and detrimental aspects of mucus-gut microbiome interactions. Studying the intricate links between the mucus barrier, the associated bacteria, and the mucosal immune system may advance our understanding of the mechanisms and inform prevention and treatment strategies in food allergy.

Identification of Two Subsets of Murine DC1 Dendritic Cells That Differ by Surface Phenotype, Gene Expression, and Function

Classical dendritic cells (cDCs) in mice have been divided into 2 major subsets based on the expression of nuclear transcription factors: a CD8⁺Irf8⁺Batf3 dependent (DC1) subset, and a CD8^-Irf4⁺ (DC2) subset. We found that the CD8⁺DC1 subset can be further divided into CD8⁺DC1a and CD8⁺DC1b subsets by differences in surface receptors, gene expression, and function. Whereas all 3 DC subsets can act alone to induce potent Th1 cytokine responses to class I and II MHC restricted peptides derived from ovalbumin (OVA) by OT-I and OT-II transgenic T cells, only the DC1b subset could effectively present glycolipid antigens to natural killer T (NKT) cells. Vaccination with OVA protein pulsed DC1b and DC2 cells were more effective in reducing the growth of the B16-OVA melanoma as compared to pulsed DC1a cells in wild type mice. In conclusion, the Batf3-/- dependent DC1 cells can be further divided into two subsets with different immune functional profiles in vitro and in vivo.

Bioderived materials that disarm the gut mucosal immune system: Potential lessons from commensal microbiota

Over the course of evolution, mammals and gut commensal microbes have adapted to coexist with each other. This homeostatic coexistence is dependent on an intricate balance between tolerogenic and inflammatory responses directed towards beneficial, commensal microbes and pathogenic intruders, respectively. Immune tolerance towards the gut microflora is largely sustained by immunomodulatory molecules produced by the commensals, which protect the bacteria from immune advances and maintain the gut's unique tolerogenic microenvironment, as well as systemic homeostasis. The identification and characterization of commensal-derived, tolerogenic molecules could lead to their utilization in biomaterials-inspired delivery schemes involving nano/microparticles or hydrogels, and potentially lead to the next generation of commensal-derived therapeutics. Moreover, gut-on-chip technologies could augment the discovery and characterization of influential commensals by providing realistic in vitro models conducive to finicky microbes. In this review, we provide an overview of the gut immune system, describe its intricate relationships with the microflora and identify major genera involved in maintaining tolerogenic responses and peripheral homeostasis. More relevant to biomaterials, we discuss commensal-derived molecules that are known to interface with immune cells and discuss potential strategies for their incorporation into biomaterial-based strategies aimed at culling inflammatory diseases. We hope this review will bridge the current findings in gut immunology, microbiology and biomaterials and spark further investigation into this emerging field. STATEMENT OF SIGNIFICANCE: Despite its tremendous potential to culminate into revolutionary therapeutics, the synergy between immunology, microbiology, and biomaterials has only been explored at a superficial level. Strategic incorporation of biomaterial-based technologies may be necessary to fully characterize and capitalize on the rapidly growing repertoire of immunomodulatory molecules derived from commensal microbes. Bioengineers may be able to combine state-of-the-art delivery platforms with immunomodulatory cues from commensals to provide a more holistic approach to combating inflammatory disease. This interdisciplinary approach could potentiate a neoteric field of research - "commensal-inspired" therapeutics with the promise of revolutionizing the treatment of inflammatory disease.

The Multiple Faces of Integrin-ECM Interactions in Inflammatory Bowel Disease

Inflammatory Bowel Disease (IBD) comprises a series of chronic and relapsing intestinal diseases, with Crohn's disease and ulcerative colitis being the most common. The abundant and uncontrolled deposition of extracellular matrix, namely fibrosis, is one of the major hallmarks of IBD and is responsible for the progressive narrowing and closure of the intestine, defined as stenosis. Although fibrosis is usually considered the product of chronic inflammation, the substantial failure of anti-inflammatory therapies to target and reduce fibrosis in IBD suggests that fibrosis might be sustained in an inflammation-independent manner. Pharmacological therapies targeting integrins have recently shown great promise in the treatment of IBD. The efficacy of these therapies mainly relies on their capacity to target the integrin-mediated recruitment and functionality of the immune cells at the damage site. However, by nature, integrins also act as mechanosensitive molecules involved in the intracellular transduction of signals and modifications originating from the extracellular matrix. Therefore, understanding integrin signaling in the context of IBD may offer important insights into mechanisms of matrix remodeling, which are uncoupled from inflammation and could underlie the onset and persistency of intestinal fibrosis. In this review, we present the currently available knowledge on the role of integrins in the etiopathogenesis of IBD, highlighting their role in the context of immune-dependent and independent mechanisms.

Dual targeting of lymphocyte homing and retention through α4β7 and αEβ7 inhibition in inflammatory bowel disease

Anti-integrins are therapeutically effective for inflammatory bowel disease, yet the relative contribution of α4β7 and αEβ7 to gut lymphocyte trafficking is not fully elucidated. Here, we evaluate the effect of α4β7 and αEβ7 blockade using a combination of murine models of gut trafficking and longitudinal gene expression analysis in etrolizumab-treated patients with Crohn's disease (CD). Dual blockade of α4β7 and αEβ7 reduces CD8+ T cell accumulation in the gut to a greater extent than blockade of either integrin alone. Anti-αEβ7 reduces epithelial:T cell interactions and promotes egress of activated T cells from the mucosa into lymphatics. Inflammatory gene expression is greater in human intestinal αEβ7+ T cells. Etrolizumab-treated patients with CD display a treatment-specific reduction in inflammatory and cytotoxic intraepithelial lymphocytes (IEL) genes. Concurrent blockade of α4β7 and αEβ7 promotes reduction of cytotoxic IELs and inflammatory T cells in the gut mucosa through a stepwise inhibition of intestinal tissue entry and retention.

A literature review on large intestinal hyperelastic constitutive modeling

Impacts, traumas and strokes are spontaneously life-threatening, but chronic symptoms strangle patient every day. Colorectal tissue mechanics in such chronic situations not only regulates the physio-psychological well-being of the patient, but also confirms the level of comfort and post-operative clinical outcomes. Numerous uniaxial and multiaxial tensile experiments on healthy and affected samples have evidenced significant differences in tissue mechanical behavior and strong colorectal anisotropy across each layer in thickness direction and along the length. Furthermore, this study reviewed various forms of passive constitutive models for the highly fibrous colorectal tissue ranging from the simplest linearly elastic and the conventional isotropic hyperelastic to the most sophisticated second harmonic generation image based anisotropic mathematical formulation. Under large deformation, the isotropic description of tissue mechanics is unequivocally ineffective which demands a microstructural based tissue definition. Therefore, the information collected in this review paper would present the current state-of-the-art in colorectal biomechanics and profoundly serve as updated computational resources to develop a sophisticated characterization of colorectal tissues.

The Importance of Metabolism for Immune Homeostasis in Allergic Diseases

There is increasing evidence that the metabolic status of T cells and macrophages is associated with severe phenotypes of chronic inflammation, including allergic inflammation. Metabolic changes in immune cells have a crucial role in their inflammatory or regulatory responses. This notion is reinforced by metabolic diseases influencing global energy metabolism, such as diabetes or obesity, which are known risk factors of severity in inflammatory conditions, due to the metabolic-associated inflammation present in these patients. Since several metabolic pathways are closely tied to T cell and macrophage differentiation, a better understanding of metabolic alterations in immune disorders could help to restore and modulate immune cell functions. This link between energy metabolism and inflammation can be studied employing animal, human or cellular models. Analytical approaches rank from classic immunological studies to integrated analysis of metabolomics, transcriptomics, and proteomics. This review summarizes the main metabolic pathways of the cells involved in the allergic reaction with a focus on T cells and macrophages and describes different models and platforms of analysis used to study the immune system and its relationship with metabolism.

Clickable Vitamins as a New Tool to Track Vitamin A and Retinoic Acid in Immune Cells

The vitamin A derivative, retinoid acid (RA) is key player in guiding adaptive mucosal immune responses. However, data on the uptake and metabolism of vitamin A within human immune cells has remained largely elusive because retinoids are small, lipophilic molecules which are difficult to detect. To overcome this problem and to be able to study the effect of vitamin A metabolism in human immune cell subsets, we have synthesized novel bio-orthogonal retinoid-based probes (clickable probes), which are structurally and functionally indistinguishable from vitamin A. The probes contain a functional group (an alkyne) to conjugate to a fluorogenic dye to monitor retinoid molecules in real-time in immune cells. We demonstrate, by using flow cytometry and microscopy, that multiple immune cells have the capacity to internalize retinoids to varying degrees, including human monocyte-derived dendritic cells (DCs) and naïve B lymphocytes. We observed that naïve B cells lack the enzymatic machinery to produce RA, but use exogenous retinoic acid to enhance CD38 expression. Furthermore, we showed that human DCs metabolize retinal into retinoic acid, which in co-culture with naïve B cells led to of the induction of CD38 expression. These data demonstrate that in humans, DCs can serve as an exogenous source of RA for naïve B cells. Taken together, through the use of clickable vitamins our data provide valuable insight in the mechanism of vitamin A metabolism and its importance for human adaptive immunity.

Tissue-Specific Contributions to Control of T Cell Immunity

T cells are critical for orchestrating appropriate adaptive immune responses and maintaining homeostasis in the face of persistent nonpathogenic Ags. T cell function is controlled in part by environmental signals received upon activation and derived from the tissue environment in which Ag is encountered. Indeed, tissue-specific environments play important roles in controlling the T cell response to Ag, and recent evidence suggests that tissue draining lymph nodes can mirror those local differences. Thus, tissue-specific immunity may begin at priming in secondary lymph nodes, where local signals have an important role in T cell fate. In this study, we discuss the tissue-specific signals that may impact T cell differentiation and function, including the microbiome, metabolism, and tissue-specific innate cell imprinting. We argue that these individual contributions create tissue-specific niches that likely play important roles in T cell differentiation and function controlling the outcome of the response to Ags.

Group 3 Innate Lymphoid Cells Program a Distinct Subset of IL-22BP-Producing Dendritic Cells Demarcating Solitary Intestinal Lymphoid Tissues

Solitary intestinal lymphoid tissues such as cryptopatches (CPs) and isolated lymphoid follicles (ILFs) constitute steady-state activation hubs containing group 3 innate lymphoid cells (ILC3) that continuously produce interleukin (IL)-22. The outer surface of CPs and ILFs is demarcated by a poorly characterized population of CD11c⁺ cells. Using genome-wide single-cell transcriptional profiling of intestinal mononuclear phagocytes and multidimensional flow cytometry, we found that CP- and ILF-associated CD11c⁺ cells were a transcriptionally distinct subset of intestinal cDCs, which we term CIA-DCs. CIA-DCs required programming by CP- and ILF-resident CCR6⁺ ILC3 via lymphotoxin-β receptor signaling in cDCs. CIA-DCs differentially expressed genes associated with immunoregulation and were the major cellular source of IL-22 binding protein (IL-22BP) at steady state. Mice lacking CIA-DC-derived IL-22BP exhibited diminished expression of epithelial lipid transporters, reduced lipid resorption, and changes in body fat homeostasis. Our findings provide insight into the design principles of an immunoregulatory checkpoint controlling nutrient absorption.

TTP-mediated regulation of mRNA stability in immune cells contributes to adaptive immunity, immune tolerance and clinical applications

Dendritic cells (DCs) form a sentinel network to induce protective immunity against pathogens or self-tolerance. mRNA stability is an important part of the post-transcriptional regulation (PTR) that controls the maturation and function of DCs. In this review, we summarize the effects of TTP-mediated regulation of mRNA stability in DCs, focusing on DC maturation and antigen presentation, T cell activation and differentiation, immune tolerance and inflammation. We also discuss the potential DC-based immune treatment for HIV⁺ patients through regulation of mRNA stability. This review proposes the regulation of mRNA stability as a novel immune therapy for various inflammatory diseases, such as arthritis and dermatitis.