Oral tolerance to food protein

Lactobacillus Casei Zhang Alleviates Shrimp Tropomyosin-Induced Food Allergy by Switching Antibody Isotypes through the NF-κB-Dependent Immune Tolerance

SCOPE

Shellfish allergy is an important cause of food allergy, and tropomyosin (TM) is the major allergen within shellfish. Probiotics are safe bacteria that benefit host health and nutrition and is proposed as a novel approach for treating immunological diseases, including food allergies.

METHODS AND RESULTS

The probiotic strain Lactobacillus casei Zhang (LcZ) isolated from koumiss is investigated for its capacity to modulate food allergy induced by TM in BALB/c mice. Oral administration of LcZ attenuated allergy symptoms and intestinal epithelial damage. Furthermore, flow cytometry, real-time quantitative PCR, and ELISA demonstrated that LcZ administration altered the development and function of dendritic cells (DCs), T cells, and B cells, finally resulting in the change of TM-specific antibody isotypes into a tolerogenic pattern. Moreover, an in vitro spleen cell culture model reveals that LcZ directly modulates regulatory tolerogenic DC and T cell development, dependent on the activation of the nuclear factor kappa B (NF-κB) signaling pathway.

CONCLUSION

This work indicates the ability of LcZ to alleviate TM-induced food allergy and demonstrates the involvement of the tolerogenic immune cells and NF-κB signaling pathway, indicating LcZ to be a potential immunomodulator and immunotherapy assistor.

Human Intestinal Mononuclear Phagocytes in Health and Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is a complex immune-mediated disease of the gastrointestinal tract that increases morbidity and negatively influences the quality of life. Intestinal mononuclear phagocytes (MNPs) have a crucial role in maintaining epithelial barrier integrity while controlling pathogen invasion by activating an appropriate immune response. However, in genetically predisposed individuals, uncontrolled immune activation to intestinal flora is thought to underlie the chronic mucosal inflammation that can ultimately result in IBD. Thus, MNPs are involved in fine-tuning mucosal immune system responsiveness and have a critical role in maintaining homeostasis or, potentially, the emergence of IBD. MNPs include monocytes, macrophages and dendritic cells, which are functionally diverse but highly complementary. Despite their crucial role in maintaining intestinal homeostasis, specific functions of human MNP subsets are poorly understood, especially during diseases such as IBD. Here we review the current understanding of MNP ontogeny, as well as the recently identified human intestinal MNP subsets, and discuss their role in health and IBD.

MuSK EAMG: Immunological Characterization and Suppression by Induction of Oral Tolerance

Myasthenia gravis (MG) with antibodies to the muscle-specific receptor tyrosine kinase (MuSK) is a distinct sub-group of MG, affecting 5–8% of all MG patients. MuSK, a receptor tyrosine kinase, is expressed at the neuromuscular junctions (NMJs) from the earliest stages of synaptogenesis and plays a crucial role in the development and maintenance of the NMJ. MuSK-MG patients are more severely affected and more refractory to treatments currently used for MG. Most patients require long-term immunosuppression, stressing the need for improved treatments. Ideally, preferred treatments should specifically delete the antigen-specific autoimmune response, without affecting the entire immune system. Mucosal tolerance, induced by oral or nasal administration of an auto-antigen through the mucosal system, resulting in an antigen-specific immunological systemic hyporesponsiveness, might be considered as a treatment of choice for MuSK-MG. In the present study we have characterized several immunological parameters of murine MuSK-EAMG and have employed induction of oral tolerance in mouse MuSK-EAMG, by feeding with a recombinant MuSK protein one week before disease induction. Such a treatment has been shown to attenuate MuSK-EAMG. Both induction and progression of disease were ameliorated following oral treatment with the recombinant MuSK fragment, as indicated by lower clinical scores and lower anti-MuSK antibody titers.

Coumarin alleviates ovalbumin-induced food anaphylaxis in a mouse model by affecting mast cell function

Coumarin is an important organic heterocyclic compound with a wide range of sources in nature. It plays an important role in the drug discovery process due to its existence in diverse biologically active compounds and its broad bioactivity. In this study, the anti-allergic activity of coumarin was evaluated using an ovalbumin (OVA)-induced mouse food allergy model and an immunoglobulin (Ig)E mediated mouse bone marrow-derived mast cell (BMMC) model. Coumarin could alleviate the OVA-induced allergic symptoms, decrease the diarrhea rates, and promote the rectal temperature rise in allergic mice. Moreover, coumarin had the ability to reduce the levels of histamine and mouse mast cell proteinases, inhibit OVA-specific IgE, and significantly decrease the population of mast cells in the spleen and mesenteric lymph nodes. Coumarin could also significantly suppress mast cell-dependent passive cutaneous anaphylaxis. Additionally, the number of mature BMMCs was decreased as coumarin caused the suppression of c-KIT receptors. Furthermore, coumarin up-regulated the apoptosis of OVA-activated BMMCs in a concentration-dependent manner. In conclusion, coumarin displayed effective anti-food allergy activity via the regulation of mast cell function and numbers. Coumarin and its derivatives provide a new direction for the development of anti-food allergic drug components.

Goblet cell associated antigen passages support the induction and maintenance of oral tolerance

Tolerance to innocuous antigens from the diet and the commensal microbiota is a fundamental process essential to health. Why tolerance is efficiently induced to substances arising from the hostile environment of the gut lumen is incompletely understood but may be related to how these antigens are encountered by the immune system. We observed that goblet cell associated antigen passages (GAPs), but not other pathways of luminal antigen capture, correlated with the acquisition of luminal substances by lamina propria (LP) antigen presenting cells (APCs) and with the sites of tolerance induction to luminal antigens. Strikingly this role extended beyond antigen delivery. The GAP function of goblet cells facilitated maintenance of pre-existing LP T regulatory cells (Tregs), imprinting LP-dendritic cells with tolerogenic properties, and facilitating LP macrophages to produce the immunomodulatory cytokine IL-10. Moreover, tolerance to dietary antigen was impaired in the absence of GAPs. Thus, by delivering luminal antigens, maintaining pre-existing LP Tregs, and imprinting tolerogenic properties on LP-APCs GAPs support tolerance to substances encountered in the hostile environment of the gut lumen.

Impact of Antiretroviral Therapy Duration on HIV-1 Infection of T Cells within Anatomic Sites

Understanding the impact of antiretroviral therapy (ART) duration on HIV-infected cells is critical for developing successful curative strategies. To address this issue, we conducted a cross-sectional/inter-participant genetic characterization of HIV-1 RNA from pre- and on-therapy plasmas and HIV-1 DNA from CD4⁺ T cell subsets derived from peripheral blood (PB), lymph node (LN), and gut tissues of 26 participants after 3 to 17.8 years of ART. Our studies revealed in four acute/early participants who had paired PB and LN samples a substantial reduction in the proportion of HIV-infected cells per year on therapy within the LN. Extrapolation to all 12 acute/early participants estimated a much smaller reduction in the proportion of HIV-1-infected cells within LNs per year on therapy that was similar to that in the participants treated during chronic infection. LN-derived effector memory T (T_EM) cells contained HIV-1 DNA that was genetically identical to viral sequences derived from pre- and on-therapy plasma samples. The proportion of identical HIV-1 DNA sequences increased within PB-derived T_EM cells. However, the infection frequency of T_EM cells in PB was stable, indicating that cellular proliferation that compensates for T cell loss over time contributes to HIV-1 persistence. This study suggests that ART reduces HIV-infected T cells and that clonal expansion of HIV-infected cells maintains viral persistence. Importantly, LN-derived T_EM cells are a probable source of HIV-1 genomes capable of producing infectious HIV-1 and should be targeted by future curative strategies.IMPORTANCE HIV-1 persists as an integrated genome in CD4⁺ memory T cells during effective therapy, and cessation of current treatments results in resumption of viral replication. To date, the impact of antiretroviral therapy duration on HIV-infected CD4⁺ T cells and the mechanisms of viral persistence in different anatomic sites is not clearly elucidated. In the current study, we found that treatment duration was associated with a reduction in HIV-infected T cells. Our genetic analyses revealed that CD4⁺ effector memory T (T_EM) cells derived from the lymph node appeared to contain provirus that was genetically identical to plasma-derived virions. Moreover, we found that cellular proliferation counterbalanced the decay of HIV-infected cells throughout therapy. The contribution of cellular proliferation to viral persistence is particularly significant in T_EM cells. Our study emphasizes the importance of HIV-1 intervention and provides new insights into the location of memory T cells infected with HIV-1 DNA, which is capable of contributing to viremia.

Guidance factors orchestrating regulatory T cell positioning in tissues during development, homeostasis, and response

Over their lifetime, regulatory T cells (Treg) recalibrate their expression of trafficking receptors multiple times as they progress through development, respond to immune challenges, or adapt to the requirements of functioning in various non-lymphoid tissue environments. These trafficking receptors, which include chemokine receptors and other G-protein coupled receptors, integrins, as well as selectins and their ligands, enable Treg not only to enter appropriate tissues from the bloodstream via post-capillary venules, but also to navigate these tissues to locally execute their immune-regulatory functions, and finally to seek out the right antigen-presenting cells and interact with these, in part in order to receive the signals that sustain their survival, proliferation, and functional activity, in part in order to execute their immuno-regulatory function by altering antigen presenting cell function. Here, we will review our current knowledge of when and in what ways Treg alter their trafficking properties. We will focus on the chemokine system and try to identify specialized, non-redundant roles of individual receptors as well as similarities and differences to the conventional T cell compartment.

Interaction between food antigens and the immune system: Association with autoimmune disorders

It has been shown that environmental factors such as infections, chemicals, and diet play a major role in autoimmune diseases; however, relatively little attention has been given to food components as the most prevalent modifiers of these afflictions. This review summarizes the current body of knowledge related to different mechanisms and associations between food proteins/peptides and autoimmune disorders. The primary factor controlling food-related immune reactions is the oral tolerance mechanism. The failure of oral tolerance triggers immune reactivity against dietary antigens, which may initiate or exacerbate autoimmune disease when the food antigen shares homology with human tissue antigens. Because the conformational fit between food antigens and a host's self-determinants has been determined for only a few food proteins, we examined evidence related to the reaction of affinity-purified disease-specific antibody with different food antigens. We also studied the reaction of monoclonal or polyclonal tissue-specific antibodies with various food antigens and the reaction of food-specific antibodies with human tissue antigens. Examining the assembled information, we postulated that chemical modification of food proteins by different toxicants in food may result in immune reaction against modified food proteins that cross-react with tissue antigens, resulting in autoimmune reactivity. Because we are what our microbiome eats, food can change the gut commensals, and toxins can breach the gut barrier, penetrating into different organs where they can initiate autoimmune response. Conversely, there are also foods and supplements that help maintain oral tolerance and microbiome homeostasis. Understanding the potential link between specific food consumption and autoimmunity in humans may lay the foundation for further research about the proper diet in the prevention of autoimmune diseases.

Ginger Increases ALDH1A1 Expression and Enhances Retinoic Acid Signaling in a Human Colonic Epithelial Cell Line

Aldehyde dehydrogenase 1A1 (ALDH1A1) in intestinal epithelial cells (IECs) plays a critical role in regulating immune responses through the production of retinoic acid (RA). However, little is known about its regulation by dietary components. We previously demonstrated that kakkonto, a Japanese traditional herbal medicine, and its constituent puerarin induce the expression of ALDH1A1 mRNA in colonic IECs and thereby attenuate food allergy symptoms in mice. This study aims to investigate the cellular responses of IECs to ALDH1A1 expression as a result of natural food components. The seven medicinal herbs that compose kakkonto were used to treat cultured an IEC line: Caco-2 cells. Expressions levels of ALDH1A1 were analyzed in Caco-2 cells by quantitative RT-PCR, immunocytochemistry and western blotting. Ginger increased the expression levels of ALDH1A1 mRNA and protein in Caco-2 cells. In addition, ginger significantly upregulated the gene expression of retinoic acid receptor (RAR) alpha (RARA), thereby enhancing RA signaling. Furthermore, ginger downregulated the expression of histone deacetylase (HDAC)2 (HDAC2) and HDAC3 in Caco-2 cells. The present study suggests the possibility that food ingredients such as a ginger modulate vitamin A metabolism in the gut through the regulation of RA synthesis, which may contribute to RA-mediated regulation of immune responses and the regulation of allergic inflammation.

Management of Cow's Milk Allergy from an Immunological Perspective: What Are the Options?

The immunological mechanism underlying Immunoglobuline E (IgE)-mediated cow’s milk allergy has been subject to investigations for many years. Identification of the key immune cells (mast cells, B cells) and molecules (IgE) in the allergic process has led to the understanding that avoidance of IgE-crosslinking epitopes is effective in the reduction of allergic symptoms but it cannot be envisioned as a treatment. For the treatment and prevention of IgE-mediated cow’s milk allergy, it is thought that the induction of a sustained state of immunological tolerance is needed. In this review, we will discuss various approaches aimed at achieving immunological tolerance and their success. Furthermore, we will speculate on the involved immunological mechanism.

Class-switch recombination to IgA in the Peyer's patches requires natural thymus-derived Tregs and appears to be antigen independent

Our understanding of how class-switch recombination (CSR) to IgA occurs in the gut is still incomplete. Earlier studies have indicated that Tregs are important for IgA CSR and these cells were thought to transform into follicular helper T cells (Tfh), responsible for germinal center formation in the Peyer's patches (PP). Following adoptive transfer of T-cell receptor-transgenic (TCR-Tg) CD4 T cells into nude mice, we unexpectedly found that oral immunization did not require an adjuvant to induce strong gut IgA and systemic IgG responses, suggesting an altered regulatory environment in the PP. After sorting of splenic TCR-Tg CD4 T cells into CD25⁺ or CD25^- cells we observed that none of these fractions supported a gut IgA response, while IgG responses were unperturbed in mice receiving the CD25^- cell fraction. Hence, while Tfh functions resided in the CD25^- fraction the IgA CSR function in the PP was dependent on CD25⁺ Foxp3⁺ Tregs, which were found to be Helios⁺ neuropilin-1⁺ thymus-derived Tregs. This is the first study to demonstrate that Tfh and IgA CSR functions are indeed, unique, and separate functions in the PP with the former being TCR-dependent while the latter appeared to be antigen independent.

Development of the equine gut microbiota

Shortly after birth the mammalian gut is colonized, by a transient microbiota, highly susceptible to environment and diet, that eventually stabilizes and becomes the resident gut microbiota. In a window of opportunity during the colonization, oral tolerance is established towards resident bacteria. In this study, the development of the equine gut microbiota was investigated in ten foals from parturition until post weaning. We found great differences in the core species of the gut microbiota composition between time-matched samples on Day 7 and 20 post-partum. Between day 20 and Day 50 post-partum, we saw the gut microbiota became increasingly dominated by fiber fermenting species. After Day 50, no significant changes in species abundance were observed. Gene expression analysis of pro- and anti-inflammatory cytokines in the blood revealed no significant changes before and after weaning. In summary, relative stability of the gut microbiota was reached within 50 days post-partum and, weaning did not have a major impact on the microbial composition.

Polysaccharide A-Dependent Opposing Effects of Mucosal and Systemic Exposures to Human Gut Commensal Bacteroides fragilis in Type 1 Diabetes

Bacteroides fragilis (BF) is an integral component of the human colonic commensal microbiota. BF is also the most commonly isolated organism from clinical cases of intra-abdominal abscesses, suggesting its potential to induce proinflammatory responses upon accessing the systemic compartment. Hence, we examined the impact of mucosal and systemic exposures to BF on type 1 diabetes (T1D) incidence in NOD mice. The impact of intestinal exposure to BF under a chemically induced enhanced gut permeability condition, which permits microbial translocation, in T1D was also examined. While oral administration of heat-killed (HK) BF to prediabetic mice caused enhanced immune regulation and suppression of autoimmunity, resulting in delayed hyperglycemia, mice that received HK BF by intravenous injection showed rapid disease progression. Importantly, polysaccharide A-deficient BF failed to produce these opposing effects upon oral and systemic deliveries. Furthermore, BF-induced modulation of disease progression was observed in wild-type, but not TLR2-deficient, NOD mice. Interestingly, oral administration of BF under enhanced gut permeability conditions resulted in accelerated disease progression and rapid onset of hyperglycemia in NOD mice. Overall, these observations suggest that BF-like gut commensals can cause proinflammatory responses upon gaining access to the systemic compartment and contribute to T1D in at-risk subjects.

TLRs toll for Tregs

Discussion on TLR3 triggering in CD4 T cells induces IFN beta and IL10-producing iTregs that suppress food allergy.

Oral Tolerance Induction to Newly Introduced Allergen is Favored by a Transforming Growth Factor-β-Enriched Formula

Food allergies have become a major healthcare concern, hence preventive efforts to ensure oral tolerance induction to newly introduced antigens are particularly relevant. Given that transforming growth factor-β (TGF-β) plays a key role in immune tolerance, we tested whether an infant formula enriched with TGF-β would improve oral tolerance induction. A partially hydrolyzed whey protein-based formula was enriched with cow's-milk-derived TGF-β (TGF-β-enriched formula) by adding a specific whey protein isolate (WPI). The manufacturing process was optimized to achieve a concentration of TGF-β within the range of human breast milk concentrations. Protection from allergic sensitization and immune response was assessed in a mouse model. Adult mice received the TGF-β-enriched formula, a control non-enriched formula, or water ad libitum for 13 days before sensitization and suboptimal tolerization to ovalbumin (OVA). When compared to non-tolerized mice, suboptimally-tolerized mice supplemented with the TGF-β-enriched formula showed significantly lower levels of total immunoglobulin-E (IgE) and OVA-specific (IgG1). Mouse mast-cell protease-1 (mMCP-1) and cytokine levels were also significantly decreased in suboptimally-tolerized mice fed the TGF-β-enriched formula. In conclusion, oral supplementation with cow's-milk-derived TGF-β decreased allergic responses to newly introduced allergens and thus reduced the risk of developing food allergy.

The Functional Power of the Human Milk Proteome

Human milk is the most complete and ideal form of nutrition for the developing infant. The composition of human milk consistently changes throughout lactation to meet the changing functional needs of the infant. The human milk proteome is an essential milk component consisting of proteins, including enzymes/proteases, glycoproteins, and endogenous peptides. These compounds may contribute to the healthy development in a synergistic way by affecting growth, maturation of the immune system, from innate to adaptive immunity, and the gut. A comprehensive overview of the human milk proteome, covering all of its components, is lacking, even though numerous analyses of human milk proteins have been reported. Such data could substantially aid in our understanding of the functionality of each constituent of the proteome. This review will highlight each of the aforementioned components of human milk and emphasize the functionality of the proteome throughout lactation, including nutrient delivery and enhanced bioavailability of nutrients for growth, cognitive development, immune defense, and gut maturation.

Raw Cow's Milk Reduces Allergic Symptoms in a Murine Model for Food Allergy-A Potential Role For Epigenetic Modifications

Epidemiological studies identified raw cow's milk consumption as an important environmental exposure that prevents allergic diseases. In the present study, we investigated whether raw cow's milk has the capacity to induce tolerance to an unrelated, non-milk, food allergen. Histone acetylation of T cell genes was investigated to assess potential epigenetic regulation. Female C3H/HeOuJ mice were sensitized and challenged to ovalbumin. Prior to sensitization, the mice were treated with raw milk, processed milk, or phosphate-buffered saline for eight days. Allergic symptoms were assessed after challenge and histone modifications in T cell-related genes of splenocyte-derived CD4⁺ T cells and the mesenteric lymph nodes were analyzed after milk exposure and after challenge. Unlike processed milk, raw milk decreased allergic symptoms. After raw milk exposure, histone acetylation of Th1-, Th2-, and regulatory T cell-related genes of splenocyte-derived CD4⁺ T cells was higher than after processed milk exposure. After allergy induction, this general immune stimulation was resolved and histone acetylation of Th2 genes was lower when compared to processed milk. Raw milk reduces allergic symptoms to an unrelated, non-milk, food allergen in a murine model for food allergy. The activation of T cell-related genes could be responsible for the observed tolerance induction, which suggested that epigenetic modifications contribute to the allergy-protective effect of raw milk.

Inflammation triggers immediate rather than progressive changes in monocyte differentiation in the small intestine

Bone marrow-derived circulating monocytes contribute to the replenishment and maintenance of the intestinal macrophage population. Intestinal monocytes undergo context-dependent phenotypic and functional adaptations to either maintain local immune balance or support intestinal inflammation. Here we use monocyte adoptive transfer to dissect the dynamics of monocyte-to-macrophage differentiation in normal and inflamed small intestine. We find that during homeostasis CCR2 and β7-integrin mediate constitutive homing of monocytes to the gut. By contrast, intestinal inflammation increases monocyte recruitment via CCR2, but not β7-integrin. In the non-inflamed intestine, monocytes gradually differentiate to express genes typically associated with tolerogenic macrophage functions. Conversely, immediately upon entry into the inflamed intestine, monocytes adapt a different expression pattern in a partly Trem-1-dependent manner. Our observations suggest that inflammation fundamentally changes the kinetics and modalities of monocyte differentiation in tissues.

Bone marrow-derived monocytes are recruited to the gut to replenish the local macrophage pool. Here the authors show that, while such replenishment constitutively occur under homeostasis, gut inflammation induces an immediate, Trem1-related transcription change to recruited monocyte to enable a context-dependent modulation of macrophage functions.

Frontline Science: Abnormalities in the gut mucosa of non-obese diabetic mice precede the onset of type 1 diabetes

Alterations in the composition of the intestinal microbiota have been associated with development of type 1 diabetes (T1D), but little is known about changes in intestinal homeostasis that contribute to disease pathogenesis. Here, we analyzed oral tolerance induction, components of the intestinal barrier, fecal microbiota, and immune cell phenotypes in non-obese diabetic (NOD) mice during disease progression compared to non-obese diabetes resistant (NOR) mice. NOD mice failed to develop oral tolerance and had defective protective/regulatory mechanisms in the intestinal mucosa, including decreased numbers of goblet cells, diminished mucus production, and lower levels of total and bacteria-bound secretory IgA, as well as an altered IEL profile. These disturbances correlated with bacteria translocation to the pancreatic lymph node possibly contributing to T1D onset. The composition of the fecal microbiota was altered in pre-diabetic NOD mice, and cross-fostering of NOD mice by NOR mothers corrected their defect in mucus production, indicating a role for NOD microbiota in gut barrier dysfunction. NOD mice had a reduction of CD103⁺ dendritic cells (DCs) in the MLNs, together with an increase of effector Th17 cells and ILC3, as well as a decrease of Th2 cells, ILC2, and Treg cells in the small intestine. Importantly, most of these gut alterations precede the onset of insulitis. Disorders in the intestinal mucosa of NOD mice can potentially interfere with the development of T1D due the close relationship between the gut and the pancreas. Understanding these early alterations is important for the design of novel therapeutic strategies for T1D prevention.

Reovirus: Friend and Foe

Purpose of Review

Mammalian orthoreovirus (reovirus) is a powerful tool for studying viral replication and pathogenesis. Most reovirus infections are subclinical, however recent work has catapulted reovirus into the clinical spotlight.

Recent Findings

Owing to its capacity to kill cancer cells more efficiently than normal cells, reovirus is under development as a therapeutic for a variety of cancers. New efforts have focused on genetically engineering reovirus to increase its oncolytic capacity, and determining how reovirus potentiates immunotherapy. Other recent studies highlight a potential role for reovirus in celiac disease (CeD). Using mouse models of CeD, reovirus caused loss of oral tolerance to dietary antigens, opening the possibility that reovirus could trigger CeD in humans.

Summary

We will focus on new developments in reovirus oncolysis and studies suggesting a role for reovirus as a trigger for celiac disease (CeD) that make reovirus a potential friend and foe to human health.

Plant cell-made protein antigens for induction of Oral tolerance

The gut associated lymphoid tissue has effective mechanisms in place to maintain tolerance to food antigens. These can be exploited to induce antigen-specific tolerance for the prevention and treatment of autoimmune diseases and severe allergies and to prevent serious immune responses in protein replacement therapies for genetic diseases. An oral tolerance approach for the prevention of peanut allergy in infants proved highly efficacious and advances in treatment of peanut allergy have brought forth an oral immunotherapy drug that is currently awaiting FDA approval. Several other protein antigens made in plant cells are in clinical development. Plant cell-made proteins are protected in the stomach from acids and enzymes after their oral delivery because of bioencapsulation within plant cell wall, but are released to the immune system upon digestion by gut microbes. Utilization of fusion protein technologies facilitates their delivery to the immune system, oral tolerance induction at low antigen doses, resulting in efficient induction of FoxP3⁺ and latency-associated peptide (LAP)⁺ regulatory T cells that express immune suppressive cytokines such as IL-10. LAP and IL-10 expression represent potential biomarkers for plant-based oral tolerance. Efficacy studies in hemophilia dogs support clinical development of oral delivery of bioencapsulated antigens to prevent anti-drug antibody formation. Production of clinical grade materials in cGMP facilities, stability of antigens in lyophilized plant cells for several years when stored at ambient temperature, efficacy of oral delivery of human doses in large animal models and lack of toxicity augur well for clinical advancement of this novel drug delivery concept.

Helios Deficiency Predisposes the Differentiation of CD4+Foxp3- T Cells into Peripherally Derived Regulatory T Cells

The transcription factor Helios is expressed in a large percentage of Foxp3⁺ regulatory T (Treg) cells and is required for the maintenance of their suppressive phenotype, as mice with a selective deficiency of Helios in Treg cells spontaneously develop autoimmunity. However, mice with a deficiency of Helios in all T cells do not exhibit autoimmunity, despite the defect in the suppressor function of their Treg cell population, suggesting that Helios also functions in non-Treg cells. Although Helios is expressed in a small subset of CD4⁺Foxp3^- and CD8⁺ T cells and its expression is upregulated upon T cell activation, its function in non-Treg cells remains unknown. To examine the function of Helios in CD4⁺Foxp3^- T cells, we transferred Helios-sufficient or -deficient naive CD4⁺Foxp3^- TCR transgenic T cells to normal recipients and examined their capacity to respond to their cognate Ag. Surprisingly, Helios-deficient CD4⁺ T cells expanded and differentiated into Th1 or Th2 cytokine-producing effectors in a manner similar to wild-type TCR transgenic CD4⁺ T cells. However, the primed Helios-deficient cells failed to expand upon secondary challenge with Ag. The tolerant state of the Helios-deficient memory T cells was not cell-intrinsic but was due to a small population of Helios-deficient naive T cells that had differentiated into Ag-specific peripheral Treg cells that suppressed the recall response in an Ag-specific manner. These findings demonstrate that Helios plays a role in the determination of CD4⁺ T cell fate.

Immunodietica: A data-driven approach to investigate interactions between diet and autoimmune disorders

Autoimmunity is on the rise around the globe. Diet has been proposed as a risk factor for autoimmunity and shown to modulate the severity of several autoimmune disorders. Yet, the interaction between diet and autoimmunity in humans remains largely unstudied. Here, we systematically interrogated commonly consumed animals and plants for peptide epitopes previously implicated in human autoimmune disease. A total of fourteen species investigated could be divided into three broad categories regarding their content in human autoimmune epitopes, which we represented using a new metric, the Gershteyn-Ferreira index (GF index). Strikingly, pig contains a disproportionately high number of unique autoimmune epitopes compared to all other species analyzed. This work uncovers a potential new link between pork consumption and autoimmunity in humans and lays the foundation for future studies on the impact of diet on the pathogenesis and progression of autoimmune disorders.

Bioadhesive Food Protein Nanoparticles as Pediatric Oral Drug Delivery System

The goal of this study was to develop bioadhesive food protein nanoparticles using zein (Z), a hydrophobic corn protein, as the core and whey protein (WP) as the shell for oral pediatric drug delivery applications. Lopinavir (LPV), an antiretroviral drug, and fenretinide, an investigational anticancer agent, were used as model drugs in the study. The particle size of ZWP nanoparticles was in the range of 200-250 nm, and the drug encapsulation efficiency was >70%. The nanoparticles showed sustained drug release in simulated gastrointestinal fluids. ZWP nanoparticles enhanced the permeability of LPV and fenretinide across Caco-2 cell monolayers. In both ex vivo and in vivo studies, ZWP nanoparticles were found to be strongly bioadhesive. ZWP nanoparticles enhanced the oral bioavailability of LPV and fenretinide by 4 and 7-fold, respectively. ZWP nanoparticles also significantly increased the half-life of both drugs. The nanoparticles did not show any immunogenicity in mice. Overall, the study demonstrates the feasibility of developing safe and effective food protein-based nanoparticles for pediatric oral drug delivery.

Short-chain fatty acids: Bacterial messengers modulating the immunometabolism of T cells

Short-chain fatty acids (SCFAs) are mainly generated by bacterial fermentation of non-digestible carbohydrates such as dietary fiber. In the last decade, new investigations have revealed that SCFAs have a very specific function and serve as active microbial metabolites, which are able to modulate the function of immune cells in the intestine and other tissues. Recent studies have highlighted the immunomodulatory potential of SCFAs in several autoimmune and inflammatory disorders such as multiple sclerosis, colitis, type 1 diabetes and rheumatoid arthritis. While the SCFA-mediated activation of GPR41/GPR43 signalling pathways and their inhibitory activity on histone deacetylases have been extensively investigated, the impact of SCFAs on the T cell metabolism is poorly understood. SCFAs induce metabolic alterations in T cells by enhancing the activity of the mTOR complex and by regulating their glucose metabolism. Once taken up into T lymphocytes, SCFA-derived acetyl groups contribute to the cellular acetyl-CoA pool, which influences the histone acetylation and cytokine gene expression. This article reviews how SCFAs modulate the metabolic status of T cells, thereby impacting on epigenetic modifications and T cell function. We will also discuss how the recent findings from SCFA biology might be utilized for potential immune therapies of various autoimmune diseases.

The Microbiome and Food Allergy

The gut-associated lymphoid tissue (GALT) faces a considerable challenge. It encounters antigens derived from an estimated 1014 commensal microbes and greater than 30 kg of food proteins yearly. It must distinguish these harmless antigens from potential pathogens and mount the appropriate host immune response. Local and systemic hyporesponsiveness to dietary antigens, classically referred to as oral tolerance, comprises a distinct complement of adaptive cellular and humoral immune responses. It is increasingly evident that a functional epithelial barrier engaged in intimate interplay with innate immune cells and the resident microbiota is critical to establishing and maintaining oral tolerance. Moreover, innate immune cells serve as a bridge between the microbiota, epithelium, and the adaptive immune system, parlaying tonic microbial stimulation into signals critical for mucosal homeostasis. Dysregulation of gut homeostasis and the subsequent disruption of tolerance therefore have clinically significant consequences for the development of food allergy.

Erythropoietin inhibits SGK1-dependent TH17 induction and TH17-dependent kidney disease

IL-17-producing CD4+ cells (TH17) are pathogenically linked to autoimmunity including to autoimmune kidney disease. Erythropoietin's (EPO) newly recognized immunoregulatory functions and its predominant intra-renal source suggested that EPO physiologically regulates TH17 differentiation, thereby serving as a barrier to the development of autoimmune kidney disease. Using in vitro studies of human and murine cells and in vivo models, we show that EPO ligation of its receptor (EPO-R) on CD4+ T cells directly inhibits TH17 generation and promotes trans-differentiation of TH17 into IL-17-FOXP3+CD4+ T cells. Mechanistically, EPO/EPO-R ligation abrogates upregulation of SGK1 gene expression and blocks p38 activity to prevent SGK1 phosphorylation, thereby inhibiting RORC-mediated transcription of IL-17 and IL-23 receptor genes. In a murine model of TH17-dependent aristolochic acid (ArA)-induced, interstitial kidney disease associated with reduced renal EPO production, we demonstrate that transgenic EPO overexpression or recombinant EPO (rEPO) administration limits TH17 formation and clinical/histological disease expression. EPO/EPO-R ligations on CD4+ T cells abrogate, while absence of T cell-expressed EPO-R augments, TH17 induction and clinical/histological expression of pristane-induced glomerulonephritis (associated with decreased intrarenal EPO). rEPO prevents spontaneous glomerulonephritis and TH17 generation in MRL-lpr mice. Together, our findings indicate that EPO physiologically and therapeutically modulate TH17 cells to limit expression of TH17-associated autoimmune kidney disease.

Myogenic tone contributes to the regulation of permeability in mesenteric microvessels

The microvascular endothelium plays a key role in regulating solute permeability in the gut, but the contribution of vascular smooth muscle to barrier function is unknown. We sought to determine the role of vascular smooth muscle and its myogenic tone in the vascular barrier to solutes in mesenteric microvessels. We determined vascular permeability to 4.4 kDa and 70 kDa dextrans in isolated mouse mesenteric arteries at increasing pressure increments. The myogenic response was simultaneously monitored using video edge-detection of vessel diameter and wall thickness. We expressed permeability as the apparent permeability coefficient, or the solute flux per second normalized to surface area and concentration gradient. We compared the effects of myogenic tone, L-type calcium channel blockade, calcium elimination, and endothelial removal on the permeability of each dextran. We found arteries resisted changes in 4.4 kDa and 70 kDa dextran permeability coefficients at intravascular pressures associated with myogenic tone. Manipulations that reduced or eliminated myogenic tone (L-type calcium channel blockade or calcium elimination) caused vasodilation and increased permeability coefficients. Thus, the maintenance of a reactive mesenteric vascular smooth muscle layer and its myogenic tone prevents increases in vascular permeability that would otherwise occur with increasing pressure. Conditions that impact vascular tone, such as trauma, stroke, or major surgery could diminish the gut-vascular barrier against dissemination of the microbiome.

Innate lymphoid cells support regulatory T cells in the intestine through interleukin-2

Interleukin (IL)-2 is a pleiotropic cytokine that is necessary to prevent chronic inflammation in the gastrointestinal tract^1-4. The protective effects of IL-2 involve the generation, maintenance and function of regulatory T (T_reg) cells^4-8, and the use of low doses of IL-2 has emerged as a potential therapeutic strategy for patients with inflammatory bowel disease⁹. However, the cellular and molecular pathways that control the production of IL-2 in the context of intestinal health are undefined. Here we show, in a mouse model, that IL-2 is acutely required to maintain T_reg cells and immunological homeostasis throughout the gastrointestinal tract. Notably, lineage-specific deletion of IL-2 in T cells did not reduce T_reg cells in the small intestine. Unbiased analyses revealed that, in the small intestine, group-3 innate lymphoid cells (ILC3s) are the dominant cellular source of IL-2, which is induced selectively by IL-1β. Macrophages in the small intestine produce IL-1β, and activation of this pathway involves MYD88- and NOD2-dependent sensing of the microbiota. Our loss-of-function studies show that ILC3-derived IL-2 is essential for maintaining T_reg cells, immunological homeostasis and oral tolerance to dietary antigens in the small intestine. Furthermore, production of IL-2 by ILC3s was significantly reduced in the small intestine of patients with Crohn's disease, and this correlated with lower frequencies of T_reg cells. Our results reveal a previously unappreciated pathway in which a microbiota- and IL-1β-dependent axis promotes the production of IL-2 by ILC3s to orchestrate immune regulation in the intestine.

Intestinal development and homeostasis require activation and apoptosis of diet-reactive T cells

The impact of food antigens on intestinal homeostasis and immune function is poorly understood. Here, we explored the impact of dietary antigens on the phenotype and fate of intestinal T cells. Physiological uptake of dietary proteins generated a highly activated CD44+Helios+CD4+ T cell population predominantly in Peyer patches. These cells are distinct from regulatory T cells and develop independently of the microbiota. Alimentation with a protein-free, elemental diet led to an atrophic small intestine with low numbers of activated T cells, including Tfh cells and decreased amounts of intestinal IgA and IL-10. Food-activated CD44+Helios+CD4+ T cells in the Peyer patches are controlled by the immune checkpoint molecule PD-1. Blocking the PD-1 pathway rescued these T cells from apoptosis and triggered proinflammatory cytokine production, which in IL-10-deficient mice was associated with intestinal inflammation. In support of these findings, our study of patients with Crohn's disease revealed significantly reduced frequencies of apoptotic CD4+ T cells in Peyer patches as compared with healthy controls. These results suggest that apoptosis of diet-activated T cells is a hallmark of the healthy intestine.

Probiotics and Prebiotics for the Amelioration of Type 1 Diabetes: Present and Future Perspectives

Type 1-diabetes (T1D) is an autoimmune disease characterized by immune-mediated destruction of pancreatic beta (β)-cells. Genetic and environmental interactions play an important role in immune system malfunction by priming an aggressive adaptive immune response against β-cells. The microbes inhabiting the human intestine closely interact with the enteric mucosal immune system. Gut microbiota colonization and immune system maturation occur in parallel during early years of life; hence, perturbations in the gut microbiota can impair the functions of immune cells and vice-versa. Abnormal gut microbiota perturbations (dysbiosis) are often detected in T1D subjects, particularly those diagnosed as multiple-autoantibody-positive as a result of an aggressive and adverse immunoresponse. The pathogenesis of T1D involves activation of self-reactive T-cells, resulting in the destruction of β-cells by CD8⁺ T-lymphocytes. It is also becoming clear that gut microbes interact closely with T-cells. The amelioration of gut dysbiosis using specific probiotics and prebiotics has been found to be associated with decline in the autoimmune response (with diminished inflammation) and gut integrity (through increased expression of tight-junction proteins in the intestinal epithelium). This review discusses the potential interactions between gut microbiota and immune mechanisms that are involved in the progression of T1D and contemplates the potential effects and prospects of gut microbiota modulators, including probiotic and prebiotic interventions, in the amelioration of T1D pathology, in both human and animal models.

Gut health and vaccination response in pre-smolt Atlantic salmon (Salmo salar) fed black soldier fly (Hermetia illucens) larvae meal

Limited availability of sustainable feed ingredients is a serious concern in salmon aquaculture. Insects may become an important, sustainable resource for expanding the raw material repertoire. Herein, we present data from an 8-week feeding trial with pre-smolt Atlantic salmon (initial body weight 49 ± 1.5 g) fed either a reference diet containing fish meal, soy protein concentrate and wheat gluten as protein sources, or a test diet wherein 85% of the protein was supplied by black soldier fly larvae meal. Possible diet effect on the systemic immune response was evaluated by measuring plasma antibody titers after vaccination against infectious pancreatic necrosis virus (IPNV). The gut health of fish was evaluated using endpoints including organ and tissue indices, histopathological parameters and gene expression. Both diets induced the same level of antibody responses against IPNV. In fish fed the reference diet, the histological examination of the pyloric caeca mucosa showed clear hyper-vacuolization suggestive of lipid accumulation in enterocytes, whereas this was less pronounced in the insect meal fed fish. Expression of genes relevant to lipid metabolism confirmed these histological findings. Immune and barrier-function gene expression profiles were both generally not affected by diet. However, the fish fed insect meal showed increased expression of genes indicative of stress response, immune tolerance and increased detoxification activity. In summary, our results showed no indications that dietary inclusion of insect meal affected the gut health of Atlantic salmon negatively. The insect meal based diet seemed to reduce excessive lipid deposition in the pyloric caeca and stimulate xenobiotic metabolism.

The microbiome and immunodeficiencies: Lessons from rare diseases

Primary immunodeficiencies (PIDs) are inherited disorders of the immune system, associated with a considerable increase in susceptibility to infections. PIDs can also predispose to malignancy, inflammation and autoimmunity. There is increasing awareness that some aspects of the immune dysregulation in PIDs may be linked to intestinal microbiota. Indeed, the gut microbiota and its metabolites have been shown to influence immune functions and immune homeostasis both locally and systemically. Recent studies have indicated that genetic defects causing PIDs lead to perturbations in the conventional mechanisms underlying homeostasis in the gut, resulting in poor immune surveillance at the intestinal barrier, which associates with altered intestinal permeability and bacterial translocation. Consistently, a substantial proportion of PID patients presents with clinically challenging IBD-like pathology. Here, we describe the current body of literature reporting on dysbiosis of the gut microbiota in different PIDs and how this can be either the result or cause of immune dysregulation. Further, we report how infections in PIDs enhance pathobionts colonization and speculate how, in turn, pathobionts may be responsible for increased disease susceptibility and secondary infections in these patients. The potential relationship between the microbial composition in the intestine and other sites, such as the oral cavity and skin, is also highlighted. Finally, we provide evidence, in preclinical models of PIDs, for the efficacy of microbiota manipulation to ameliorate disease complications, and suggest that the potential use of dietary intervention to correct dysbiotic flora in PID patients may hold promise.

Cytokines and Soluble Receptors in Breast Milk as Enhancers of Oral Tolerance Development

The postpartum period is an important window during which environmental factors can shape the life-long health of the infant. This time period often coincides with substantial milk consumption either in the form of breast milk or from cow's milk sources, such as infant formulas. Although breast milk is the most beneficial source of nutrients for infants during the first 6 months after birth, its role in regulating food allergy development, through regulation of oral tolerance, is still controversial. Breast milk contains several factors that can impact mucosal immune function, including immune cells, antibodies, microbiota, oligosaccharides, cytokines, and soluble receptors. However, there is considerable variation in the assessed levels of cytokines and soluble receptors between studies and across the lactation period. Most of these cytokines and soluble receptors are absent, or only found in limited quantities, in commercial baby formulas. Differences in content of these pluripotent factors, which impact on both the mother and the neonate, could contribute to the controversy surrounding the role of breast milk regulating oral tolerance. This review highlights current knowledge about the importance of cytokines and soluble receptors in breast milk on the development of oral tolerance and tolerance-relateddisorders. Understanding the mechanisms by which such milk components might promote oral tolerance could aid in the development of improved strategies for allergy prevention.

Efficient oral vaccination by bioengineering virus-like particles with protozoan surface proteins

Intestinal and free-living protozoa, such as Giardia lamblia, express a dense coat of variant-specific surface proteins (VSPs) on trophozoites that protects the parasite inside the host’s intestine. Here we show that VSPs not only are resistant to proteolytic digestion and extreme pH and temperatures but also stimulate host innate immune responses in a TLR-4 dependent manner. We show that these properties can be exploited to both protect and adjuvant vaccine antigens for oral administration. Chimeric Virus-like Particles (VLPs) decorated with VSPs and expressing model surface antigens, such as influenza virus hemagglutinin (HA) and neuraminidase (NA), are protected from degradation and activate antigen presenting cells in vitro. Orally administered VSP-pseudotyped VLPs, but not plain VLPs, generate robust immune responses that protect mice from influenza infection and HA-expressing tumors. This versatile vaccine platform has the attributes to meet the ultimate challenge of generating safe, stable and efficient oral vaccines.

Giardia lamblia express a dense coat of variant-specific surface proteins (VSPs) on trophozoites that protects the parasite inside the host´s intestine. Here the authors show that stability and immunomodulatory properties of VSPs can be exploited to both protect and adjuvant vaccine antigens for oral administration.

Healthy infants harbor intestinal bacteria that protect against food allergy

There has been a striking generational increase in life-threatening food allergies in Westernized societies^1,2 One hypothesis to explain this rising prevalence is that 21^st century lifestyle practices, including misuse of antibiotics, dietary changes, and higher rates of Caesarean birth and formula feeding have altered intestinal bacterial communities; early life alterations may be particularly detrimental.^3,4 To better understand how commensal bacteria regulate food allergy in humans we colonized germ free (GF) mice with feces from healthy or cow’s milk allergic (CMA) infants ⁵. We show here that GF mice colonized with bacteria from healthy, but not CMA, infants were protected against anaphylactic responses to a cow’s milk allergen. Differences in bacterial composition separated the healthy and CMA populations in both the human donors and the colonized mice. Healthy and CMA colonized mice also exhibited unique transciptome signatures in the ileal epithelium. Correlation of ileal bacteria with genes upregulated in the ileum of healthy or CMA colonized mice identified a Clostridial species, Anaerostipes caccae, that protected against an allergic response to food. Our findings demonstrate that intestinal bacteria are critical for regulating allergic responses to dietary antigens and suggest that interventions that modulate bacterial communities may be therapeutically relevant for food allergy.

Mechanisms by which gut microorganisms influence food sensitivities

Finely tuned mechanisms enable the gastrointestinal tract to break down dietary components into nutrients without mounting, in the majority of cases, a dysregulated immune or functional host response. However, adverse reactions to food have been steadily increasing, and evidence suggests that this process is environmental. Adverse food reactions can be divided according to their underlying pathophysiology into food intolerances, when, for instance, there is deficiency of a host enzyme required to digest the food component, and food sensitivities, when immune mechanisms are involved. In this Review, we discuss the clinical and experimental evidence for enteric infections and/or alterations in the gut microbiota in inciting food sensitivity. We focus on mechanisms by which microorganisms might provide direct pro-inflammatory signals to the host promoting breakdown of oral tolerance to food antigens or indirect pathways that involve the metabolism of protein antigens and other dietary components by gut microorganisms. Better understanding of these mechanisms will help in the development of preventive and therapeutic strategies for food sensitivities.

Shaping the Gut Microbiota by Breastfeeding: The Gateway to Allergy Prevention?

Evidence is accumulating that demonstrates the importance of the gut microbiota in health and diseases such as allergy. Recent studies emphasize the importance of the "window of opportunity" in early life, during which interventions altering the gut microbiota induce long-term effects. The neonate's gut microbiota composition and metabolism could therefore play an essential role in allergic disease risk. Breastfeeding shapes the gut microbiota in early life, both directly by exposure of the neonate to the milk microbiota and indirectly, via maternal milk factors that affect bacterial growth and metabolism such as human milk oligosaccharides, secretory IgA, and anti-microbial factors. The potential of breastmilk to modulate the offspring's early gut microbiota is a promising tool for allergy prevention. Here, we will review the existing evidence demonstrating the impact of breastfeeding on shaping the neonate's gut microbiota and highlight the potential of this strategy for allergy prevention.

Commensal Bacteria-Specific CD4+ T Cell Responses in Health and Disease

Over the course of evolution, mammalian body surfaces have adapted their complex immune system to allow a harmless coexistence with the commensal microbiota. The adaptive immune response, in particular CD4+ T cell-mediated, is crucial to maintain intestinal immune homeostasis by discriminating between harmless (e.g., dietary compounds and intestinal microbes) and harmful stimuli (e.g., pathogens). To tolerate food molecules and microbial components, CD4+ T cells establish a finely tuned crosstalk with the environment whereas breakdown of these mechanisms might lead to chronic disease associated with mucosal barriers and beyond. How commensal-specific immune responses are regulated and how these molecular and cellular mechanisms can be manipulated to treat chronic disorders is yet poorly understood. In this review, we discuss current knowledge of the regulation of commensal bacteria-specific CD4+ T cells. We place particular focus on the key role of commensal-specific CD4+ T cells in maintaining tolerance while efficiently eradicating local and systemic infections, with a focus on factors that trigger their aberrant activation.

The role of regulatory T cells in the acquisition of tolerance to food allergens in children

Food allergy is a pathological immune reaction that identifies certain harmless food proteins, usually tolerated by the majority of the people, as a threat. The prevalence of these food allergies is increasing worldwide and currently affects 8% of children. Exacerbated reactions to milk, egg and peanut are the most frequent in the pediatric population. It is well known that allergic diseases are a type 2 T-helper (Th2) immune response, characterized by the elevated production of IgE antibodies. However, little is known about the immune mechanisms responsible for the development of clinical tolerance toward food allergens. Recent studies have suggested the key role of regulatory T cells (Tregs) in controlling allergic inflammation. In this review, we discuss the importance of Tregs in the pathogenesis of food allergy and the acquisition of oral tolerance in children. Further investigation in this area will be crucial for the identification of predictive markers and the development of new therapies, which will represent a clinical and social benefit for these allergic diseases.

Goblet cells: multifaceted players in immunity at mucosal surfaces

Goblet cells (GCs) are specialized epithelial cells that line multiple mucosal surfaces and have a well-appreciated role in barrier maintenance through the secretion of mucus. Moreover, GCs secrete anti-microbial proteins, chemokines, and cytokines demonstrating functions in innate immunity beyond barrier maintenance. Recently it was appreciated that GCs can form goblet cell-associated antigen passages (GAPs) and deliver luminal substances to underlying lamina propria (LP) antigen-presenting cells (APCs) in a manner capable of inducing adaptive immune responses. GCs at other mucosal surfaces share characteristics with the GAP forming intestinal GCs, suggesting that GAP formation may not be restricted to the gut, and that GCs may perform this gatekeeper function at other mucosal surfaces. Here we review observations of how GCs contribute to immunity at mucosal surfaces through barrier maintenance, the delivery of luminal substances to APCs, interactions with APCs, and secretion of factors modulating immune responses.

Neuroimmune Communication in Health and Disease

The immune and nervous systems are tightly integrated, with each system capable of influencing the other to respond to infectious or inflammatory perturbations of homeostasis. Recent studies demonstrating the ability of neural stimulation to significantly reduce the severity of immunopathology and consequently reduce mortality have led to a resurgence in the field of neuroimmunology. Highlighting the tight integration of the nervous and immune systems, afferent neurons can be activated by a diverse range of substances from bacterial-derived products to cytokines released by host cells. While activation of vagal afferents by these substances dominates the literature, additional sensory neurons are responsive as well. It is becoming increasingly clear that although the cholinergic anti-inflammatory pathway has become the predominant model, a multitude of functional circuits exist through which neuronal messengers can influence immunological outcomes. These include pathways whereby efferent signaling occurs independent of the vagus nerve through sympathetic neurons. To receive input from the nervous system, immune cells including B and T cells, macrophages, and professional antigen presenting cells express specific neurotransmitter receptors that affect immune cell function. Specialized immune cell populations not only express neurotransmitter receptors, but express the enzymatic machinery required to produce neurotransmitters, such as acetylcholine, allowing them to act as signaling intermediaries. Although elegant experiments have begun to decipher some of these interactions, integration of these molecules, cells, and anatomy into defined neuroimmune circuits in health and disease is in its infancy. This review describes these circuits and highlights continued challenges and opportunities for the field.

Food-specific IgGs Are Highly Increased in the Sera of Patients with Inflammatory Bowel Disease and Are Clinically Relevant to the Pathogenesis

Objective Dietary antigens are common luminal antigens in the gastrointestinal tract and have been considered to contribute to the pathogenesis of inflammatory bowel disease (IBD). We analyzed the levels of food-specific IgGs against a variety of dietary antigens, explored the clinical relevance of food allergy to the pathogenesis of IBD, and investigated whether or not infliximab (IFX) treatment could regulate the immune responses induced by dietary antigens. Methods A total of 301 IBD patients, including 201 patients with Crohn's disease (CD) and 100 patients with ulcerative colitis (UC), were recruited, and their serum food-specific IgGs against 14 food antigens were detected by a semi-quantitative enzyme linked immunosorbent assay (ELISA). Total serum IgG and IgE levels were measured by immunonephelometry and fluorescent enzyme immunoassay, respectively. Simultaneously, the relevant medical records and clinical data were collected for further analyses. Results Food-specific IgGs against egg, milk, wheat, corn, rice, tomato, codfish, and soybean antigens were found to be significantly increased in the sera of CD patients compared with UC patients and healthy controls (p<0.01). The levels of total serum IgG and IgE were also significantly higher in CD patients than in healthy controls (p<0.01). The titers of corn- and tomato-specific IgGs were found to be significantly correlated with total serum IgG in CD patients (p<0.05), while the titers of egg-, milk-, and wheat-specific IgGs were correlated with total serum IgE (p<0.05). Interestingly, IFX therapy was able to down-regulate the food-specific IgG-mediated immune response markedly in active CD patients. Conclusion Food-specific IgGs against egg, milk, wheat, corn, rice, tomato, codfish, and soybean are highly increased in the sera of CD patients. IFX treatment was able to down-regulate the levels of food-specific IgGs by suppressing intestinal inflammation and promoting mucosal healing. Therefore, food-specific IgGs may serve as an important approach in the diagnosis and management of food allergy in IBD.