CD4+CD25+ regulatory T cells suppress mast cell degranulation and allergic responses through OX40-OX40L interaction. Immunity. 2008;29:771-781. [PMID: 18993084 DOI: 10.1016/j.immuni.2008.08.018]

Innate lymphoid cells in immunoglobulin E-mediated food allergy

PURPOSE OF REVIEW

Recognition of the importance of innate lymphoid cells (ILCs) in the immune mechanisms of food allergy has grown in recent years. This review summarizes recent findings of ILCs in immunoglobulin E (IgE)-mediated food allergy. New research on ILCs in the context of the microbiome and other atopic diseases are also considered with respect to how they can inform understanding of the role of ILCs in food allergy.

RECENT FINDINGS

ILCs can mediate allergic and tolerogenic responses through multiple pathways. A novel subset of interleukin (IL)-10 producing ILC2s are associated with tolerance following immunotherapy to grass pollen, house dust mite allergy and lipid transfer protein allergy. ILC2s can drive food allergen-specific T cell responses in an antigen-specific manner. A memory subset of ILC2s has been identified through studies of other atopic diseases and is associated with effectiveness of response to therapy.

SUMMARY

The role of ILCs in food allergy and oral tolerance is relatively understudied compared to other diseases. ILCs can modulate immune responses through several mechanisms, and it is likely that these are of importance in the context of food allergy. Better understanding of theses pathways may help to answer fundamental questions regarding the development of food allergy and lead to novel therapeutic targets and treatment.

Nano-Sized Graphene Oxide Attenuates Ovalbumin/Alum-Induced Skin Inflammation by Down-Regulating Th2 Immune Responses in Balb/c Mice

Graphene oxide (GO), a carbon-based material with oxygen-containing functional groups, can be applied in biomedicine for drug delivery, cancer therapy, and tissue regeneration. We have previously shown that nanoscale-sized graphene oxide (NGO), an oxidized graphene derivative, exhibits effective anti-inflammatory activity in a murine model of sepsis mediated by T helper (Th)1-promoting cytokines such as IFNγ and TNFα. However, whether NGO influences Th2-induced skin inflammation remains unclear. To address this issue, we employed an ovalbumin (OVA) plus aluminum hydroxide (Alum)-induced Th2-mediated skin inflammation model in conjunction with OVA-specific DO11.10 T cell receptor transgenic Balb/c mice. In vivo NGO injection upon OVA/Alum sensitization down-regulated OVA-elicited antigen-specific Th2 cells and GATA3-expressing Th2-type regulatory T cells. Next, we examined the effect of NGO injection on OVA/Alum-induced atopic dermatitis (AD)-like skin inflammation. NGO-injected mice exhibited significantly decreased Th2 disease phenotypes (e.g., a lower clinical score, decreased epidermal thickness and Th2 cell differentiation, and fewer infiltrated mast cells and basophils in skin lesions) compared with vehicle-injected control mice. Overall, our results suggest that NGOs are promising therapeutic materials for treating allergic diseases such as AD.

Costimulatory Molecule CD226 Regulates Atopic Dermatitis in a Mouse Model

This study investigated the role of CD226 in a 2,4-dinitrochlorobenzene (DNCB)-induced mouse model of atopic dermatitis. The results showed that the lack of CD226 (global and CD4+ T-cell specific) significantly increased ear thickness, reddening, swelling, and scaling of the skin as well as inflammatory cell and mast cell infiltration. RT-qPCR results demonstrated that the mRNA expressions of atopic dermatitis-related inflammatory cytokines and chemokines were markedly increased in the draining lymph nodes and lesioned ear skin tissues of global and CD4+ T-cell-specific CD226-deficient mice compared with that in control mice. In vitro assessment revealed that CD226 directly modulates TGFβ-mediated regulatory T (Treg) cell differentiation and proliferation. Notably, Treg cell-specific deletion of CD226 (Cd226fl/flFoxp3cre mice) resulted in more severe dermatitis and epidermal thickening than those observed in littermate mice upon DNCB treatment. Subsequent analysis showed that the infiltration of Treg cells in ear lesions and the number of Tregs in the spleen were significantly reduced in Cd226fl/flFoxp3cre mice after DNCB treatment. In addition, the lack of CD226 induced apoptosis of Treg cells through the activation of caspase 3. Therefore, these results suggest that CD226 has potential efficacy in atopic dermatitis, correlating with Treg cell inhibition.

A mutation in Themis contributes to anaphylaxis severity following oral peanut challenge in CC027 mice

BACKGROUND

The development of peanut allergy is due to a combination of genetic and environmental factors, although specific genes have proven difficult to identify. Previously, we reported that peanut-sensitized Collaborative Cross strain CC027/GeniUnc (CC027) mice develop anaphylaxis upon oral challenge to peanut, in contrast to C3H/HeJ (C3H) mice.

OBJECTIVE

This study aimed to determine the genetic basis of orally induced anaphylaxis to peanut in CC027 mice.

METHODS

A genetic mapping population between CC027 and C3H mice was designed to identify the genetic factors that drive oral anaphylaxis. A total of 356 CC027xC3H backcrossed mice were generated, sensitized to peanut, then challenged to peanut by oral gavage. Anaphylaxis and peanut-specific IgE were quantified for all mice. T-cell phenotyping was conducted on CC027 mice and 5 additional Collaborative Cross strains.

RESULTS

Anaphylaxis to peanut was absent in 77% of backcrossed mice, with 19% showing moderate anaphylaxis and 4% having severe anaphylaxis. There were 8 genetic loci associated with variation in response to peanut challenge-6 associated with anaphylaxis (temperature decrease) and 2 associated with peanut-specific IgE levels. There were 2 major loci that impacted multiple aspects of the severity of acute anaphylaxis, at which the CC027 allele was associated with worse outcome. At one of these loci, CC027 has a private genetic variant in the Themis gene. Consistent with described functions of Themis, we found that CC027 mice have more immature T cells with fewer CD8+, CD4+, and CD4+CD25+CD127- regulatory T cells.

CONCLUSIONS

Our results demonstrate a key role for Themis in the orally reactive CC027 mouse model of peanut allergy.

Routinely Used and Emerging Diagnostic and Immunotherapeutic Approaches for Wheat Allergy

Wheat, a component of the staple diet globally, is a common food allergen in children. The symptoms of wheat allergy (WA) range from skin rash to shortness of breath, significantly impairing quality of life. Following initial clinical suspicion, individuals may undergo routinely used allergy tests such as a wheat allergen-specific skin prick test (SPT), a blood test for specific immunoglobulin E (sIgE) levels, or oral food challenge. Conventional management of WA lies in wheat avoidance, yet accidental consumption may be inevitable owing to the ubiquity of wheat in various food products. This article aims to provide an overview of the immunologic pathway of WA, followed by its emerging diagnostic methods, namely alcohol-soluble SPT extracts, component-resolved diagnosis, and the basophil activation test (BAT). The mechanisms underlying wheat allergen-specific oral immunotherapy (OIT) as well as a summary of the efficacy, tolerability, and safety of related clinical trials will then be discussed.

Complex Role of Regulatory T Cells (Tregs) in the Tumor Microenvironment: Their Molecular Mechanisms and Bidirectional Effects on Cancer Progression

Regulatory T cells (Tregs) possess unique immunosuppressive activity among CD4-positive T cells. Tregs are ubiquitously present in mammals and function to calm excessive immune responses, thereby suppressing allergies or autoimmune diseases. On the other hand, due to their immunosuppressive function, Tregs are thought to promote cancer progression. The tumor microenvironment (TME) is a multicellular system composed of many cell types, including tumor cells, infiltrating immune cells, and cancer-associated fibroblasts (CAFs). Within this environment, Tregs are recruited by chemokines and metabolic factors and impede effective anti-tumor responses. However, in some cases, their presence can also improve patient's survival rates. Their functional consequences may vary across tumor types, locations, and stages. An in-depth understanding of the precise roles and mechanisms of actions of Treg is crucial for developing effective treatments, emphasizing the need for further investigation and validation. This review aims to provide a comprehensive overview of the complex and multifaceted roles of Tregs within the TME, elucidating cellular communications, signaling pathways, and their impacts on tumor progression and highlighting their potential anti-tumor mechanisms through interactions with functional molecules.

The mast cell-T lymphocyte axis impacts cancer: Friend or foe?

Crosstalk between mast cells (MCs) and T lymphocytes (TLs) releases specific signals that create an environment conducive to tumor development. Conversely, they can protect against cancer by targeting tumor cells for destruction. Although their role in immunity and cancer is complex, their potential in anticancer strategies is often underestimated. When peripheral MCs are activated, they can affect cancer development. Tumor-infiltrating TLs may malfunction and contribute to aggressive cancer and poor prognoses. One promising approach for cancer patients is TL-based immunotherapies. Recent reports suggest that MCs modulate TL activity in solid tumors and may be a potential therapeutic layer in multitargeting anticancer strategies. Pharmacologically modulating MC activity can enhance the anticancer cytotoxic TL response in tumors. By identifying tumor-specific targets, it has been possible to genetically alter patients' cells into fully humanized anticancer cellular therapies for autologous transplantation, including the engineering of TLs and MCs to target and kill cancer cells. Hence, recent scientific evidence provides a broader understanding of MC-TL activity in cancer.

Potential anti-tumor effects of regulatory T cells in the tumor microenvironment: a review

Regulatory T cells (Tregs) expressing the transcription factor FoxP3 are essential for maintaining immunological balance and are a significant component of the immunosuppressive tumor microenvironment (TME). Single-cell RNA sequencing (ScRNA-seq) technology has shown that Tregs exhibit significant plasticity and functional diversity in various tumors within the TME. This results in Tregs playing a dual role in the TME, which is not always centered around supporting tumor progression as typically believed. Abundant data confirms the anti-tumor activities of Tregs and their correlation with enhanced patient prognosis in specific types of malignancies. In this review, we summarize the potential anti-tumor actions of Tregs, including suppressing tumor-promoting inflammatory responses and boosting anti-tumor immunity. In addition, this study outlines the spatial and temporal variations in Tregs function to emphasize that their predictive significance in malignancies may change. It is essential to comprehend the functional diversity and potential anti-tumor effects of Tregs to improve tumor therapy strategies.

Anti-allergic effect of Cyclopia (honeybush) extracts via anti-degranulation activity in a murine allergy model for inhaled antigen

The anti-allergic effects of extracts prepared from two species of honeybush, Cyclopia genistoides and Cyclopia subternata, were demonstrated in vivo in a murine allergy model for inhaled antigen induced with ovalbumin (OVA) inhalation to mimic pollen allergy. Intake of the extracts increased the production of OVA-specific immunoglobulin (Ig) E (IgE), IgG1, and IgG2a antibodies in serum and significantly suppressed anaphylactic reaction-induced body temperature decline. Moreover, the extracts significantly inhibited antigen-antibody-induced degranulation in RBL-2H3 cells. They also inhibited body temperature decline when the allergic mice were given them after antigen sensitization, indicating that anti-degranulation activity is the major mechanism underlying the anti-allergic effect of Cyclopia extracts. Despite their qualitative and quantitative differences in phenolic composition, the two extracts exhibited similar effects, suggesting that several active compounds might be involved in the activity. Therefore, oral administration of either Cyclopia extract potentially exerts a systemic anti-allergic effect, supporting the increased consumption of honeybush tea for general wellness and improved quality of life.

Engineering nanoparticle therapeutics for food allergy

Food allergy is a growing public health issue among children and adults that can lead to life-threatening anaphylaxis following allergen exposure. The criterion standard for disease management includes food avoidance and emergency epinephrine administration because current allergen-specific immunotherapy treatments are limited by adverse events and unsustained desensitization. A promising approach to remedy these shortcomings is the use of nanoparticle-based therapies that disrupt disease-driving immune mechanisms and induce more sustained tolerogenic immune pathways. The pathophysiology of food allergy includes multifaceted interactions between effector immune cells, including lymphocytes, antigen-presenting cells, mast cells, and basophils, mainly characterized by a TH2 cell response. Regulatory T cells, TH1 cell responses, and suppression of other major allergic effector cells have been found to be major drivers of beneficial outcomes in these nanoparticle therapies. Engineered nanoparticle formulations that have shown efficacy at reducing allergic responses and revealed new mechanisms of tolerance include polymeric-, lipid-, and emulsion-based nanotherapeutics. This review highlights the recent engineering design of these nanoparticles, the mechanisms induced by them, and their future potential therapeutic targets.

Phase 1 trial supports safety and mechanism of action of peptide immunotherapy for peanut allergy

BACKGROUND

Food allergy is a leading cause of anaphylaxis worldwide. Allergen-specific immunotherapy is the only treatment shown to modify the natural history of allergic disease, but application to food allergy has been hindered by risk of severe allergic reactions and short-lived efficacy. Allergen-derived peptides could provide a solution. PVX108 comprises seven short peptides representing immunodominant T-cell epitopes of major peanut allergens for treatment of peanut allergy.

METHODS

Pre-clinical safety of PVX108 was assessed using ex vivo basophil activation tests (n = 185). Clinical safety and tolerability of single and repeat PVX108 doses were evaluated in a first-in-human, randomized, double-blind, placebo-controlled trial in peanut-allergic adults (46 active, 21 placebo). The repeat-dose cohort received six doses over 16 weeks with safety monitored to 21 weeks. Exploratory immunological analyses were performed at pre-dose, Week 21 and Month 18 after treatment.

RESULTS

PVX108 induced negligible activation of peanut-sensitised basophils. PVX108 was safe and well tolerated in peanut-allergic adults. There were no treatment-related hypersensitivity events or AEs of clinical concern. The only events occurring more frequently in active than placebo were mild injection site reactions. Exploratory immunological analyses revealed a decrease in the ratio of ST2+ Th2A:CCR6+ Th17-like cells within the peanut-reactive Th pool which strengthened following treatment.

CONCLUSION

This study supports the concept that PVX108 could provide a safe alternative to whole peanut immunotherapies and provides evidence of durable peanut-specific T-cell modulation. Translation of these findings to clinical efficacy in ongoing Phase 2 trials would provide important proof-of-concept for using peptides to treat food allergy.

Classification of regulatory T cells and their role in myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MIRI) is closely related to the final infarct size in acute myocardial infarction (AMI). Therefore, reducing MIRI can effectively improve the prognosis of AMI patients. At the same time, the healing process after AMI is closely related to the local inflammatory microenvironment. Regulatory T cells (Tregs) can regulate various physiological and pathological immune inflammatory responses and play an important role in regulating the immune inflammatory response after AMI. However, different subtypes of Tregs have different effects on MIRI, and the same subtype of Tregs may also have different effects at different stages of MIRI. This article systematically reviews the classification and function of Tregs, as well as the role of various subtypes of Tregs in MIRI. A comprehensive understanding of the role of each subtype of Tregs can help design effective methods to control immune reactions, reduce MIRI, and provide new potential therapeutic options for AMI.

Biomarkers of Autoimmune Chronic Spontaneous Urticaria

PURPOSEOF REVIEW

Chronic spontaneous urticaria and chronic inducible urticaria (CSU/CindU) are caused by mast cell and basophil activation leading to degranulation and the release of histamine and several other mediators. Three kinds of factors can trigger mast cells in CSU: (1) activation of stimulating receptor(s) on the mast cell membrane, (2) upregulation of certain receptor(s), and (3) intracellular dysregulation in signaling with overexpression of the spleen tyrosine kinase (SYK) or reduced activation of the inhibitory Src homology 2 (SH2)-containing inositol phosphatases (SHIP)-related pathways. In CSU, two major endotypes exist based on the primary receptor activating mechanism: type I hypersensitivity (IgE-mediated, directed against auto-allergens) and type IIb (autoimmune, via IgG autoantibodies directed against IgE or the IgE-receptor). Their treatment responses vary. We discuss in vitro and in vivo biomarkers.

RECENT FINDINGS

Patients with auto-allergic CSU have clinical characteristics that can distinguish them partly from those with autoimmune CSU. Most importantly, their disease generally presents a less aggressive course, a better response to second generation (up-dosed) antihistamines and a good response to omalizumab, if necessary. Meanwhile, autoimmune CSU/CindU patients fare less well and often need immunosuppressive drugs. Biomarkers that might help endotype CSU/CindU patients and select the most appropriate treatment, dose, and duration, e.g., for autoallergic CSU, high total IgE and IgE against auto-allergens; for autoimmune CSU, low IgE, basopenia, and IgG against autoantigens like thyroid peroxidase and a positive autologous serum skin test (but sometimes also positive in autoallergy). Some biomarkers are easily accessible but of low specificity; others are highly specific but more futuristic.

Research progress in the pathogenesis of chronic urticaria

Chronic urticaria is very common in clinic, but its pathogenesis is not fully elucidated. Most patients can't find the exact cause, resulting in misdiagnosis or delayed treatment. Previous studies have found that mast cell activation is the central link in the pathogenesis of chronic urticaria. Genetics, autoimmune, coagulation disorders, and infection may also be involved in the pathophysiological process of chronic urticaria. With the deepening of research, more immune and non-immune mechanisms have been gradually revealed in the pathogenesis of chronic urticaria, such as the interaction of immune cells in the microenvironment of urticaria, intestinal flora and metabolism, neuroimmunity, environmental factors and hormones. Clarifying the pathogenesis of chronic urticaria will help to find more treatment targets and provide more diversified ideas for clinical diagnosis and treatment.

A mutation in Themis contributes to peanut-induced oral anaphylaxis in CC027 mice

Background

The development of peanut allergy is due to a combination of genetic and environmental factors, although specific genes have proven difficult to identify. Previously, we reported that peanut-sensitized CC027/GeniUnc (CC027) mice develop anaphylaxis upon oral challenge to peanut, unlike C3H/HeJ (C3H) mice.

Objective

To determine the genetic basis of orally-induced anaphylaxis to peanut in CC027 mice.

Methods

A genetic mapping population between CC027 and C3H mice was designed to identify the genetic factors that drive oral anaphylaxis. A total of 356 CC027xC3H backcrossed mice were generated, sensitized to peanut, then challenged to peanut by oral gavage. Anaphylaxis and peanut-specific IgE were quantified for all mice. T-cell phenotyping was conducted on CC027 and five additional CC strains.

Results

Anaphylaxis to peanut was absent in 77% of backcrossed mice, with 19% showing moderate anaphylaxis, and 4% having severe anaphylaxis. A total of eight genetic loci were associated with variation in response to peanut challenge, six associated with anaphylaxis (temperature decrease) and two associated with peanut-specific IgE levels. There were two major loci that impacted multiple aspects of the severity of acute anaphylaxis, at which the CC027 allele was associated with worse outcome. At one of these loci, CC027 has a private genetic variant in the Themis (thymocyte-expressed molecule involved in selection) gene. Consistent with Themis' described functions, we found that CC027 have more immature T cells with fewer CD8+, CD4+, and CD4+CD25+CD127- regulatory T cells.

Conclusion

Our results demonstrate a key role for Themis in the orally-reactive CC027 mouse model of peanut allergy.

Frenemies in the Microenvironment: Harnessing Mast Cells for Cancer Immunotherapy

Tumor development, progression, and resistance to therapies are influenced by the interactions between tumor cells and the surrounding microenvironment, comprising fibroblasts, immune cells, and extracellular matrix proteins. In this context, mast cells (MCs) have recently emerged as important players. Yet, their role is still controversial, as MCs can exert pro- or anti-tumor functions in different tumor types depending on their location within or around the tumor mass and their interaction with other components of the tumor microenvironment. In this review, we describe the main aspects of MC biology and the different contribution of MCs in promoting or inhibiting cancer growth. We then discuss possible therapeutic strategies aimed at targeting MCs for cancer immunotherapy, which include: (1) targeting c-Kit signaling; (2) stabilizing MC degranulation; (3) triggering activating/inhibiting receptors; (4) modulating MC recruitment; (5) harnessing MC mediators; (6) adoptive transferring of MCs. Such strategies should aim to either restrain or sustain MC activity according to specific contexts. Further investigation would allow us to better dissect the multifaceted roles of MCs in cancer and tailor novel approaches for an "MC-guided" personalized medicine to be used in combination with conventional anti-cancer therapies.

Diverse Role of OX40 on T Cells as a Therapeutic Target for Skin Diseases

OX40 is an important costimulatory molecule for T-cell expansion and survival. Because OX40 is expressed on most T-cell subsets, it is an attractive therapeutic target for a variety of T-cell‒mediated diseases. Clinical trials are already underway for some skin inflammatory diseases. In this review, we present various observations that improve our understanding of how OX40-targeted therapy can be applied for skin inflammatory diseases, such as atopic dermatitis and psoriasis, T helper (Th)2- and Th17-mediated diseases, respectively. The important OX40/OX40L-mediated interaction between T cells and other immune cells is also discussed in terms of skin autoimmune diseases, such as alopecia areata and pemphigus. Regulatory T cells (Tregs) highly express OX40, and the skin harbors a large Treg population; thus, understanding how OX40-targeted treatment acts on Tregs is vital for the development of therapeutic strategies for various skin diseases.

The Controversial Role of Intestinal Mast Cells in Colon Cancer

Mast cells are tissue-resident sentinels involved in large number of physiological and pathological processes, such as infection and allergic response, thanks to the expression of a wide array of receptors. Mast cells are also frequently observed in a tumor microenvironment, suggesting their contribution in the transition from chronic inflammation to cancer. In particular, the link between inflammation and colorectal cancer development is becoming increasingly clear. It has long been recognized that patients with inflammatory bowel disease have an increased risk of developing colon cancer. Evidence from experimental animals also implicates the innate immune system in the development of sporadically occurring intestinal adenomas, the precursors to colorectal cancer. However, the exact role of mast cells in tumor initiation and growth remains controversial: mast cell-derived mediators can either exert pro-tumorigenic functions, causing the progression and spread of the tumor, or anti-tumorigenic functions, limiting the tumor's growth. Here, we review the multifaceted and often contrasting findings regarding the role of the intestinal mast cells in colon cancer progression focusing on the molecular pathways mainly involved in the regulation of mast cell plasticity/functions during tumor progression.

Molecular docking, network pharmacology and experimental verification to explore the mechanism of Wulongzhiyangwan in the treatment of pruritus

Wulongzhiyangwan (WLZYW) is a Chinese prescription medicine for the treatment of pruritus, but its mechanism has not been clarified. The purpose of this study was to explore the mechanism of WLZYW in pruritus through network pharmacology analysis and experimental validation. The active components and corresponding targets of WLZYW were obtained from the Traditional Chinese Medicine Systematic Pharmacology (TCMSP) database. Pruritus-related targets were obtained from the GeneCards, TTD (Therapeutic Target Database), and DrugBank databases. The key compounds, core targets, main biological processes and signaling pathways related to WLZYW were identified by constructing and analyzing related networks. The binding affinity between WLZYW components and core targets was validated by AutoDock Vina software. In this study, RBL-2H3 cells were used to construct a degranulation model to simulate histamine-dependent pruritus. 10 chemical constituents, 235 targets and 3606 pruritus-related targets of WLZYW were obtained. Subsequently, 26 core targets were identified through analysis, VEGFA and AKT1 were the main candidates. A pathway enrichment analysis showed that overlapping targets were significantly enriched in the PI3K/AKT signaling pathway. A molecular docking analysis revealed tight binding of VEGF to three core compounds, kaempferol, luteolin and quercetin. Experiments showed that WZLYW inhibited mast cell degranulation, regulated VEGFa mRNA and protein expression levels by inhibiting PI3K/AKT and ERK1/2 signaling pathway activation. The mechanism of WZLYW in pruritus may be regulating VEGFa expression. Network pharmacology assays suggested that WLZYW downregulates VEGFa expression by regulating the PI3K/AKT and ERK1/2 signaling pathways in pruritis treatment.

Gut Microbiome Composition in Patients with Chronic Urticaria: A Review of Current Evidence and Data

Recent studies have linked gut microorganism composition and chronic urticaria (CU); however, the underlying mechanisms responsible for this connection are unknown. Since the human immune system is in homeostasis with microbiota, and the composition of the microbiome regulates the development and function of the immune system, it is likely that an alteration of microbiota components (a dysbiosis) could influence the course of chronic spontaneous urticaria (CSU), including disease severity, patient quality of life and treatment outcome. To date, several studies have identified changes in the gut microbiota composition of patients with CSU, though only a few have exhibited metabolic abnormalities associated with gut dysbiosis. The studies on CSU patients predominantly showed that the relative abundance of beneficial bacteria was decreased (Firmicutes and Bacteroides), while that of opportunistic bacteria was increased (Enterobacteria and Proteobacteria). In addition, serum metabolome analysis revealed that gut microbiota-associated alterations in unsaturated fatty acids and the butanoate metabolism pathway may play a role in CSU. These findings are potentially associated with inflammation mediated by the imbalance of Th1/Th2/Th17 cytokines, which might contribute to CSU pathogenesis. Further research in this field could improve clinical, diagnostic, and therapeutic approaches to patients with CSU. By applying new knowledge on gut microbial communities and metabolomics, future CSU therapies could modify the microbiota composition using agents such as probiotics or other similar agents, which, in combination with current standard therapies, could hopefully lead to a reduction in symptoms and an improved quality of life for CSU patients.

Controversial role of mast cells in NSCLC tumor progression and angiogenesis

Mast cells (MCs) are multifunctional immune cells implicated in both physiological and pathological processes. Among the latter, MCs play a crucial role in cancer. Many studies have shown a correlation between MCs and tumor progression in several solid and hematological malignancies. In particular, MCs can directly promote tumor growth via c-kit/stem cell factor-dependent signaling and via the release of histamine, which modulate tumor growth through H1 and H2 receptors. At the same time, MCs can increase tumor progression by stimulating angiogenesis via both proangiogenic cytokines stored in their cytoplasm, and by acting on the tumor microenvironment and extracellular matrix. With regard to NSCLC, the role of MCs has not yet been established, with studies showing a correlation with a poor prognosis on the one hand and suggesting a protective effect of MCs on the other hand. These controversial evidences are at least, in part, due to the heterogeneity of the studies exploring the role of MCs in NSCLC, with some studies describing only the MC count without specification of the activation and degranulation state, and without reporting the intratumoral localization and the proximity to other immune and cancer cells. A better knowledge of the role of MCs in NSCLC is mandatory, not only to define their prognostic and predictive proprieties but also because targeting them could be a possible therapeutic strategy.

Distribution of decidual mast cells in fetal growth restriction and stillbirth at (near) term

INTRODUCTION

Placental pathology and pregnancy complications are associated with unfavorable regulation of the maternal immune system. Although much research has been performed towards the role of immune cells like macrophages and T cells in this context, little is known about the presence and function of mast cells (MC). MC can be sub classified in tryptase-positive (MC_T) and tryptase- and chymase-positive (MC_TC). This study investigates the presence of MC in the decidua of pregnancies complicated by fetal growth restriction (FGR) and stillbirth (SB).

METHODS

Placental tissue from FGR (n = 250), SB (n = 64) and healthy pregnancies (n = 42) was included. Histopathological lesions were classified according to the Amsterdam Placental Workshop Group criteria. Tissue sections were stained for tryptase and chymase. Decidual MC were counted manually, and the results were expressed as number of cells/mm² decidual tissue.

RESULTS

A significant lower median number of MC_TC was found in the decidua of FGR (0.40 per mm²; p < 0.001) and SB (0.51 per mm²; p < 0.05) compared to healthy controls (1.04 per mm²). No difference in MC_T number (1.19 per mm², 1.88 per mm² and 1.37 per mm² respectively) was seen between the groups. There was no difference in number of MC_T and MC_TC between placental pathological lesions.

DISCUSSION

Our findings suggest a shift in decidual MC balance towards MC_T in pregnancy complications. No difference in numbers of MC subtypes was found to be related to histopathologic lesions.

Mast Cell Interaction with Foxp3+ Regulatory T Cells Occur in the Dermis after Initiation of IgE-Mediated Cutaneous Anaphylaxis

Mast cells (MCs) are well-known for their role in IgE-mediated cutaneous anaphylactic responses, but their regulatory functions in the skin are still under intense scrutiny. Using a Red MC and Basophil reporter (RMB) mouse allowing red fluorescent detection and diphtheria toxin mediated depletion of MCs, we investigated the interaction of MCs, Foxp3+ regulatory T lymphocytes (Tregs) and Langerhans cells (LCs) during passive cutaneous anaphylaxis (PCA) responses. Using intravital imaging we show that MCs are sessile at homeostasis and during PCA. Breeding RMB mice with Langerin-eGFP mice revealed that dermal MCs do not interact with epidermal-localized LCs, the latter showing constant sprouting of their dendrites at homeostasis and during PCA. When bred with Foxp3-eGFP mice, we found that, although a few Foxp3+ Tregs are present at homeostasis, many Tregs transiently infiltrated the skin during PCA. While their velocity during PCA was not altered, Tregs increased the duration of their contact time with MCs compared to PCA-control mice. Antibody-mediated depletion of Tregs had no effect on the intensity of PCA. Hence, the observed increase in Treg numbers and contact time with MCs, regardless of an effect on the intensity of PCA responses, suggests an anti-inflammatory role dedicated to prevent further MC activation.

The ketone body β-hydroxybutyrate mitigates ILC2-driven airway inflammation by regulating mast cell function

Ketone bodies are increasingly understood to have regulatory effects on immune cell function, with β-hydroxybutyrate (BHB) exerting a predominantly anti-inflammatory response. Dietary strategies to increase endogenous ketone body availability such as the ketogenic diet (KD) have recently been shown to alleviate inflammation of the respiratory tract. However, the role of BHB has not been addressed. Here, we observe that BHB suppresses group 2 innate lymphoid cell (ILC2)-mediated airway inflammation. Central to this are mast cells, which support ILC2 proliferation through interleukin-2 (IL-2). Suppression of the mast cell/IL-2 axis by BHB attenuates ILC2 proliferation and the ensuing type 2 cytokine response and immunopathology. Mechanistically, BHB directly inhibits mast cell function in part through GPR109A activation. Similar effects are achieved with either the KD or 1,3-butanediol. Our data reveal the protective role of BHB in ILC2-driven airway inflammation, which underscores the potential therapeutic value of ketone body supplementation for the management of asthma.

Targeting myeloid villains in the treatment with immune checkpoint inhibitors in gastrointestinal cancer

Despite the clinical outcomes being extremely limited, blocking immune inhibitory checkpoint pathways has been in the spotlight as a promising strategy for treating gastrointestinal cancer. However, a distinct strategy for the successful treatment is obviously needed in the clinical settings. Myeloid cells, such as neutrophils, macrophages, dendritic cells, and mast cells, are the majority of cellular components in the human immune system, but have received relatively less attention for the practical implementation than T cells and NK cells in cancer therapy because of concentration of the interest in development of the immune checkpoint blocking antibody inhibitors (ICIs). Abnormality of myeloid cells must impact on the entire host, including immune responses, stromagenesis, and cancer cells, leading to refractory cancer. This implies that elimination and reprogramming of the tumor-supportive myeloid villains may be a breakthrough to efficiently induce potent anti-tumor immunity in cancer patients. In this review, we provide an overview of current situation of the IC-blocking therapy of gastrointestinal cancer, including gastric, colorectal, and esophageal cancers. Also, we highlight the possible oncoimmunological components involved in the mechanisms underlying the resistance to the ICI therapy, particularly focusing on myeloid cells, including unique subsets expressing IC molecules. A deeper understanding of the molecular and cellular determinants may facilitate its practical implementation of targeting myeloid villains, and improve the clinical outcomes in the ICI therapy of gastrointestinal cancer.

Utilizing mast cells in a positive manner to overcome inflammatory and allergic diseases

Mast cells (MCs) are immune cells widely distributed in the body, accompanied by diverse phenotypes and functions. Committed mast cell precursors (MCPs) leave the bone marrow and enter the blood circulation, homing to peripheral sites under the control of various molecules from different microenvironments, where they eventually differentiate and mature. Partly attributable to the unique maturation mechanism, MCs display high functional heterogeneity and potentially plastic phenotypes. High plasticity also means that MCs can exhibit different subtypes to cope with different microenvironments, which we call “the peripheral immune education system”. Under the peripheral immune education system, MCs showed a new character from previous cognition in some cases, namely regulation of allergy and inflammation. In this review, we focus on the mucosal tissues, such as the gastrointestinal tract, to gain insights into the mechanism underlying the migration of MCs to the gut or other organs and their heterogeneity, which is driven by different microenvironments. In particular, the immunosuppressive properties of MCs let us consider that positively utilizing MCs may be a new way to overcome inflammatory and allergic disorders.

In silico Identification of Immune Cell-Types and Pathways Involved in Chronic Spontaneous Urticaria

Background

The immunopathogenesis of chronic spontaneous urticaria (CSU) is poorly understood, but recent research suggests that patients can be divided into autoallergic and autoimmune subtypes. Given that not all patients can be controlled with current treatment regimens, including anti-IgE monoclonal antibodies, a better understanding of the immune pathways involved in CSU may enable the repurposing of monoclonal antibodies used for other dermatologic diseases (e.g., Th2 and Th17 inhibitors). Therefore, we investigated the implicated immune cells and pathways by reanalyzing publicly available transcriptomic data.

Methods

Microarray data of CSU and healthy control (HC) skin and blood were obtained from the Gene Expression Omnibus (GSE72542, GSE57178). Differentially expressed genes were defined as a false discovery rate <0.05 and a |log₂ fold change| ≥1. Pathway analyses were conducted using ToppGene and KEGG. Cell-type enrichment was determined by CIBERSORT and xCell and was correlated with clinical characteristics.

Results

Th2 (IL-4/13 signaling) and Th17-related (IL-17/23 signaling) pathways were upregulated in lesional compared to non-lesional and HC samples. In non-lesional versus lesional samples, CIBERSORT analysis revealed increased regulatory T-cells (Treg) and resting mast cells. xCell analysis established that Th1 and Th2 scores were not significantly different between lesional and HC samples. However, Th2 scores in both lesional and non-lesional samples correlated positively with disease severity. Few differentially expressed genes and pathways were identified between CSU and HC blood samples.

Conclusion

Our results support the involvement of Th2 and Th17-related genes and pathways in CSU. Th2 scores associate with disease severity, which indicates the clinical relevance of these findings. Increased resting mast cell and Treg scores in non-lesional samples may suggest local suppression of wheal formation. Moreover, disease activity seemed to be restricted to the skin as there were limited findings from blood. Larger studies using next-generation sequencing will be helpful to confirm these results.

Understanding sex differences in the allergic immune response to food

Food allergies are of great public health concern due to their rising prevalence. Our understanding of how the immune system reacts to food remains incomplete. Allergic responses vary between individuals with food allergies. This variability could be caused by genetic, environmental, hormonal, or metabolic factors that impact immune responses mounted against allergens found in foods. Peanut (PN) allergy is one of the most severe and persistent of food allergies, warranting examination into how sensitization occurs to drive IgE-mediated allergic reactions. In recent years, much has been learned about the mechanisms behind the initiation of IgE-mediated food allergies, but additional questions remain. One unresolved issue is whether sex hormones impact the development of food allergies. Sex differences are known to exist in other allergic diseases, so this poses the question about whether the same phenomenon is occurring in food allergies. Studies show that females exhibit a higher prevalence of atopic conditions, such as allergic asthma and eczema, relative to males. Discovering such sex differences in allergic diseases provide a basis for investigating the mechanisms of how hormones influence the development of IgE-mediated reactions to foods. Analysis of existing food allergy demographics found that they occur more frequently in male children and adult females, which is comparable to allergic asthma. This paper reviews existing allergic mechanisms, sensitization routes, as well as how sex hormones may play a role in how the immune system reacts to common food allergens such as PN.

Epicutaneous allergen immunotherapy induces a profound and selective modulation in skin dendritic cell subsets

BACKGROUND

Epicutaneous immunotherapy (EPIT) protocols have recently been developed to restore tolerance in patients with food allergy (FA). The mechanisms by which EPIT protocols promote desensitization rely on a profound immune deviation of pathogenic T and B cell responses.

OBJECTIVE

To date, little is known about the contribution of skin dendritic cells (skDCs) to T cell remodeling and EPIT efficacy.

METHODS

We capitalized on a preclinical model of food allergy to ovalbumin (OVA) to characterize the phenotype and functions of OVA⁺ skDCs throughout the course of EPIT.

RESULTS

Our results showed that both Langerhans cells (LCs) and dermal conventional cDC1 and cDC2 subsets retained their ability to capture OVA in the skin and to migrate toward the skin-draining lymph nodes during EPIT. However, their activation/maturation status was significantly impaired, as evidenced by the gradual and selective reduction of CD86, CD40, and OVA protein expression in respective subsets. Phenotypic changes during EPIT were also characterized by a progressive diversification of single cell gene signatures within each DC subset. Interestingly, we observed that OVA⁺ LCs progressively lost their capacity to prime CD4⁺ T_EFF, but gained T_REG stimulatory properties. In contrast, cDC1 were inefficient in priming CD4⁺ T_EFF or in reactivating T_MEMin vitro, while cDC2 retained moderate stimulatory properties, and progressively biased type-2 immunity toward type-1 and type-17 responses.

CONCLUSIONS

Our results therefore emphasize that the acquisition of distinct phenotypic and functional specializations by skDCs during EPIT is at the cornerstone of the desensitization process.

Current Strategies to Modulate Regulatory T Cell Activity in Allergic Inflammation

Over the past decades, atopic diseases, including allergic rhinitis, asthma, atopic dermatitis, and food allergy, increased strongly worldwide, reaching up to 50% in industrialized countries. These diseases are characterized by a dominating type 2 immune response and reduced numbers of allergen-specific regulatory T (Treg) cells. Conventional allergen-specific immunotherapy is able to tip the balance towards immunoregulation. However, in mouse models of allergy adaptive transfer of Treg cells did not always lead to convincing beneficial results, partially because of limited stability of their regulatory phenotype activity. Besides genetic predisposition, it has become evident that environmental factors like a westernized lifestyle linked to modern sanitized living, the early use of antibiotics, and the consumption of unhealthy foods leads to epithelial barrier defects and dysbiotic microbiota, thereby preventing immune tolerance and favoring the development of allergic diseases. Epigenetic modification of Treg cells has been described as one important mechanism in this context. In this review, we summarize how environmental factors affect the number and function of Treg cells in allergic inflammation and how this knowledge can be exploited in future allergy prevention strategies as well as novel therapeutic approaches.

Plasma Metabolites and Gut Microbiota Are Associated With T cell Imbalance in BALB/c Model of Eosinophilic Asthma

The pathogenesis of allergic asthma is complex, it is usually caused by immune system imbalance. Th1, Th2, regulatory T cells (Treg) and T helper 17 (Th17) cells have an important role in the pathogenesis of eosinophilic asthma. Yet, the exact role of Th1, Th2, Treg and Th17 cells in eosinophilic asthmatic disease is not fully understood. This study used an untargeted plasma metabolomics combine 16S rDNA technology to identify new biomarkers of plasma metabolites and gut microbiota in ovalbumin-induced eosinophilic allergic asthma in BALB/c mice to further explore the biomarkers in regulating the immune balance or the immune response. We discovered that malate, l-dihydroorotate were associated with Th1/Th2 and Treg/Th17 cells balance, imidazoleacetic acid was associated with Th1/Th2 cell balance, 1,5-anhydro-d-sorbitol was associated with Treg/Th17 cell balance. The results also found that genus Candidatus Arthromitus of gut microbiota were associated with Th1/2, Treg/Th17 balance, genus Ruminiclostridium 6, they were all associated with Th1/2 and Treg/Th17 cell balance, while the gut microbiota were not associated with penh value which reflect airway hyperresponsiveness (AHR) in the eosinophilic asthma mice model. Interestingly, the plasma metabolite biomarkers of malate, l-dihydroorotate are associated with genus Ruminiclostridium 6, they were all associated with Th1/2 and Treg/Th17 cell balance, while imidazoleacetic acid is associated with genus Ruminiclostridium 6 which is associated with Th1/2 balance. Among the differential plasma metabolites, 1,5-anhydro-d-sorbitol is associated with genus Ruminiclostridium 6 and genus Candidatus Arthromitus. Among them, malate participate in the T cell activation, T cell differentiation and activation may be a new research direction in eosinophilic allergic asthma. We firstly study the gut microbiota and plasma metabolites markers of immune balance in eosinophilic asthma in mice model, laying a foundation for drug treatment in eosinophilic allergic asthma.

Neuro-allergology: Mast cell-nerve cross-talk

Mast cells (MCs) are derived from hematopoietic stem cells in the bone marrow, and their maturation is regulated by the tissue environment, such as the skin, lung and gut, leading to host defense. Peripheral nerve fibers located in various tissues are involved in diverse physiological and pathological processes. Anatomical relationships between MCs and nerve fibers were reported to have been observed in various organs. Moreover, MCs are positive for a large number of receptors for classical neurotransmitters (e.g., acetylcholine and corticotropin-releasing hormone) and neuropeptides (e.g., substance P, calcitonin gene-related peptides and hemokinin), and MC's functions are regulated by those nerve-derived factors. Also, histamine and proteases produced and released by MCs modulate nerve fiber functions. This functional cross-talk between MCs and nerve fibers can play physiological and pathological roles. MCs are key effector cells of allergic inflammation, such as atopic dermatitis, airway inflammation and food allergy. Here, we summarize and discuss the molecular mechanisms underlying the functional and anatomical cross-talk between MCs and nerve fibers in allergic inflamed tissues.

Interplay between Mast Cells and Regulatory T Cells in Immune-Mediated Cholangiopathies

Immune-mediated cholangiopathies are characterised by the destruction of small and large bile ducts causing bile acid stasis, which leads to subsequent inflammation, fibrosis, and eventual cirrhosis of the liver tissue. A breakdown of peripheral hepatic immune tolerance is a key feature of these diseases. Regulatory T cells (Tregs) are a major anti-inflammatory immune cell subset, and their quantities and functional capacity are impaired in autoimmune liver diseases. Tregs can undergo phenotypic reprogramming towards pro-inflammatory Th1 and Th17 profiles. The inflamed hepatic microenvironment influences and can impede normal Treg suppressive functions. Mast cell (MC) infiltration increases during liver inflammation, and active MCs have been shown to be an important source of pro-inflammatory mediators, thus driving pathogenesis. By influencing the microenvironment, MCs can indirectly manipulate Treg functions and inhibit their suppressive and proliferative activity. In addition, direct cell-to-cell interactions have been identified between MCs and Tregs. It is critical to consider the effects of MCs on the inflammatory milieu of the liver and their influence on Treg functions. This review will focus on the roles and crosstalk of Tregs and MCs during autoimmune cholangiopathy pathogenesis progression.

Few, but Efficient: The Role of Mast Cells in Breast Cancer and Other Solid Tumors

Tumor outcome is determined not only by cancer cell-intrinsic features but also by the interaction between cancer cells and their microenvironment. There is great interest in tumor-infiltrating immune cells, yet mast cells have been less studied. Recent work has highlighted the impact of mast cells on the features and aggressiveness of cancer cells, but the eventual effect of mast cell infiltration is still controversial. Here, we review multifaceted findings regarding the role of mast cells in cancer, with a particular focus on breast cancer, which is further complicated because of its classification into subtypes characterized by different biological features, outcome, and therapeutic strategies.

Assessment of Allergen-Responsive Regulatory T Cells in Experimental Asthma Induced in Different Mouse Strains

Background

Regulatory T cells (Tregs) are important in regulating responses to innocuous antigens, such as allergens, by controlling the Th2 response, a mechanism that appears to be compromised in atopic asthmatic individuals. Different isogenic mouse strains also have distinct immunological responses and susceptibility to the experimental protocols used to develop lung allergic inflammation. In this work, we investigated the differences in the frequency of Treg cell subtypes among A/J, BALB/c, and C57BL/6, under normal conditions and following induction of allergic asthma with ovalbumin (OVA).

Methods

Subcutaneous sensitization followed by 4 consecutive intranasal OVA challenges induced asthma characteristic changes such as airway hyperreactivity, inflammation, and production of Th2 cytokines (IL-4, IL-13, IL-5, and IL-33) in the lungs of only A/J and BALB/c but not C57BL/6 strain and evaluated by invasive whole-body plethysmography, flow cytometry, and ELISA, respectively.

Results

A/J strain naturally showed a higher frequency of CD4⁺IL-10⁺ T cells in the lungs of naïve mice compared to the other strains, accompanied by higher frequencies of CD4⁺IL-4⁺ T cells. C57BL/6 mice did not develop lung inflammation and presented higher frequency of CD4⁺CD25⁺Foxp3⁺ Treg cells in the bronchoalveolar lavage fluid (BALF) after the allergen challenge. In in vitro settings, allergen-specific stimulation of mediastinal LN (mLN) cells from OVA-challenged animals induced higher frequency of CD4⁺IL-10⁺ Treg cells from A/J strain and CD4⁺CD25⁺Foxp3⁺ from C57BL/6.

Conclusions

The observed differences in the frequencies of Treg cell subtypes associated with the susceptibility of the animals to experimental asthma suggest that CD4⁺CD25⁺Foxp3⁺ and IL-10-producing CD4⁺ Treg cells may play different roles in asthma control. Similar to asthmatic individuals, the lack of an efficient regulatory response and susceptibility to the development of experimental asthma in A/J mice further suggests that this strain could be preferably chosen in experimental models of allergic asthma.

New Therapeutic Approaches for Allergy: A Review of Cell Therapy and Bio- or Nano-Material-Based Strategies

Allergy constitutes a major health issue due to its large prevalence. The established therapeutic approaches (allergen avoidance, antihistamines, and corticosteroids) do not address the underlying causes of the pathology, highlighting the need for other long-term treatment options. Antigen-specific immunotherapy enables the long-term control of allergic diseases by promoting immunological tolerance to the allergen. However, efficacious immunotherapies are not available for all possible allergens, and the risk of undesired reactions during therapy remains a concern, especially in patients with severe allergic reactions. In this context, two types of therapeutic strategies appear especially promising for the future in the context of allergy: cell therapy and bio- or nano-material-based therapy. In this review, the main strategies developed this far in these two types of strategies are discussed, with several examples illustrating the different approaches.

Mast Cells as Important Regulators in Autoimmunity and Cancer Development

Mast cells are an essential part of the immune system and are best known as important modulators of allergic and anaphylactic immune responses. Upon activation, mast cells release a multitude of inflammatory mediators with various effector functions that can be both protective and damage-inducing. Mast cells can have an anti-inflammatory or pro-inflammatory immunological effect and play important roles in regulating autoimmune diseases including rheumatoid arthritis, type 1 diabetes, and multiple sclerosis. Importantly, chronic inflammation and autoimmunity are linked to the development of specific cancers including pancreatic cancer, prostate cancer, colorectal cancer, and gastric cancer. Inflammatory mediators released from activated mast cells regulate immune responses and promote vascular permeability and the recruitment of immune cells to the site of inflammation. Mast cells are present in increased numbers in tissues affected by autoimmune diseases as well as in tumor microenvironments where they co-localize with T regulatory cells and T effector cells. Mast cells can regulate immune responses by expressing immune checkpoint molecules on their surface, releasing anti-inflammatory cytokines, and promoting vascularization of solid tumor sites. As a result of these immune modulating activities, mast cells have disease-modifying roles in specific autoimmune diseases and cancers. Therefore, determining how to regulate the activities of mast cells in different inflammatory and tumor microenvironments may be critical to discovering potential therapeutic targets to treat autoimmune diseases and cancer.

Regulatory T Cells in Chronic Heart Failure

Heart failure is a global problem with high hospitalization and mortality rates. Inflammation and immune dysfunction are involved in this disease. Owing to their unique function, regulatory T cells (Tregs) have reacquired attention recently. They participate in immunoregulation and tissue repair in the pathophysiology of heart failure. Tregs are beneficial in heart by suppressing excessive inflammatory responses and promoting stable scar formation in the early stage of heart injury. However, in chronic heart failure, the phenotypes and functions of Tregs changed. They transformed into an antiangiogenic and profibrotic cell type. In this review, we summarized the functions of Tregs in the development of chronic heart failure first. Then, we focused on the interactions between Tregs and their target cells. The target cells of Tregs include immune cells (such as monocytes/macrophages, dendritic cells, T cells, and B cells) and parenchymal cells (such as cardiomyocytes, fibroblasts, and endothelial cells). Next-generation sequencing and gene editing technology make immunotherapy of heart failure possible. So, prospective therapeutic approaches based on Tregs in chronic heart failure had also been evaluated.

Lycopus lucidus Turcz ameliorates DNCB‑induced atopic dermatitis in BALB/c mice

Atopic dermatitis (AD) is a chronic inflammatory allergic skin disease, characterized by pruritic and eczematous skin lesions. Lycopus lucidus Turcz (LLT) is a perennial herb that has been reported to have various biological properties, including effects on blood circulation, as well as anti-inflammatory, antioxidant, anti-vascular inflammation and wound-healing effects. However, whether LLT improves dermatitis and the underlying mechanisms has yet to be determined. The aim of the present study was to determine whether LLT can improve 2,4-dinitrochlorobenzene (DNCB)-induced dermatitis and to verify the inhibitory effect of LLT on the expression of chemokines and pro-inflammatory cytokines in the HaCaT immortalized keratinocyte cell line. In addition, the anti-inflammatory function of LLT in RAW264.7 mouse macrophages was investigated. In the DNCB-induced AD mouse model, LLT inhibited infiltration by mast cells, eosinophils and CD8⁺ cells in the dorsal skin tissue of AD mice, and suppressed the expression of IgE and IL-6 in serum. In addition, LLT inhibited the phosphorylation of ERK and JNK, as well as NF-κB in skin tissue. In the HaCaT cell model induced by TNF-α/IFN-γ, LLT inhibited the expression of thymus and activation-regulated chemokine, granulocyte-macrophage colony-stimulating factor, monocyte chemoattractant protein-1, TNF-α and IL-1β, whilst inhibiting the phosphorylation of NF-κB. In addition, in the lipopolysaccharide-induced RAW 264.7 cell inflammation model, LLT inhibited the expression of TNF-α and IFN-γ, the nuclear translocation of NF-κB and the phosphorylation of ERK and JNK. These results suggested that LLT may be a promising candidate for the treatment of inflammatory dermatitis.

Demonstration and implications of IL-3 upregulation of CD25 expression on human mast cells

BACKGROUND

CD25⁺ human mast cells (huMCs) have been reported in patients with monoclonal mast cell diseases and in rare association with inflammation. However, the regulation of CD25 expression on huMCs and the possible biologic consequences remain poorly understood.

OBJECTIVE

We sought to identify conditions that would upregulate CD25 expression on huMCs and to explore possible functional implications.

METHODS

huMCs were cultured from peripheral blood progenitor cells over 6 to 8 weeks. Expression of CD25 was determined by fluorescence-activated cell sorting and soluble CD25 by ELISA. Signal transducer and activator of transcription 5 (STAT5) phosphorylation induced by IL-2 in huMCs, regulatory T (Treg) cells, or in cocultured huMCs and Treg cells was examined by fluorescence-activated cell sorting.

RESULTS

Addition of IL-3 to CD34⁺ progenitors at the initiation of huMC cultures in the presence of stem cell factor and IL-6 upregulated the expression of CD25 in developing huMCs and resulted in shedding of soluble CD25 into the media. Removal of IL-3 after the first week of culture did not affect subsequent expression of CD25. Furthermore, addition of IL-3 14 days after the initiation of the culture did not induce significant CD25 expression. Treatment with anti-IL-3 antibody or the Janus kinase inhibitor tofacitinib blocked IL-3-induced CD25 upregulation. Binding of IL-2 to CD25⁺ huMCs did not induce STAT5 phosphorylation. However, coincubation of Treg cells with CD25⁺ huMCs pretreated with IL-2 was sufficient to result in STAT5 phosphorylation in Treg cells.

CONCLUSIONS

IL-3 promotes CD25 expression and shedding by huMCs. Although CD25⁺ huMCs do not respond to IL-2, they bind IL-2 and may act as a reservoir of IL-2 to then activate lymphocytes.

Novel Approaches in the Inhibition of IgE-Induced Mast Cell Reactivity in Food Allergy

Allergy is an IgE-dependent type-I hypersensitivity reaction that can lead to life-threatening systemic symptoms such as anaphylaxis. In the pathogenesis of the allergic response, the common upstream event is the binding of allergens to specific IgE, inducing cross-linking of the high-affinity FcεRI on mast cells, triggering cellular degranulation and the release of histamine, proteases, lipids mediators, cytokines and chemokines with inflammatory activity. A number of novel therapeutic options to curb mast cell activation are in the pipeline for the treatment of severe allergies. In addition to anti-IgE therapy and allergen-specific immunotherapy, monoclonal antibodies targeted against several key Th2/alarmin cytokines (i.e. IL-4Rα, IL-33, TSLP), active modification of allergen-specific IgE (i.e. inhibitory compounds, monoclonal antibodies, de-sialylation), engagement of inhibitory receptors on mast cells and allergen-specific adjuvant vaccines, are new promising options to inhibit the uncontrolled release of mast cell mediators upon allergen exposure. In this review, we critically discuss the novel approaches targeting mast cells limiting allergic responses and the immunological mechanisms involved, with special interest on food allergy treatment.

Regulatory T Cells Exhibit Interleukin-33-Dependent Migratory Behavior during Skin Barrier Disruption

Regulatory T cells (Tregs) suppress immune responses and maintain immunological self-tolerance and homeostasis. We currently investigated relationships between skin barrier condition and Treg behavior using skin barrier-disrupted mice. Skin barrier disruption was induced by repeated topical application of 4% sodium dodecyl sulfate (SDS) on mice. The number of CD4⁺ forkhead box protein P3 (Foxp3)⁺ Tregs was higher in 4% SDS-treated skins than in controls. This increasing was correlated with the degree of acanthosis. The numbers of interleukin (IL)-10⁺ and transforming growth factor (TGF)-β⁺ Tregs also increased in 4% SDS-treated skins. Localization of IL-33 in keratinocytes shifted from nucleus to cytoplasm after skin barrier disruption. Notably, IL-33 promoted the migration of Tregs in chemotaxis assay. The skin infiltration of Tregs was cancelled in IL-33 neutralizing antibody-treated mice and IL-33 knockout mice. Thus, keratinocyte-derived IL-33 may induce Treg migration into barrier-disrupted skin to control the phase transition between healthy and inflammatory conditions.

Diversity of T Helper and Regulatory T Cells and Their Contribution to the Pathogenesis of Allergic Diseases

T helper (Th) and regulatory T (Treg) cells represent important effectors of adaptive immunity. They mediate communication between the immune system and tissue sites and thereby coordinate effective defense against environmental threats or maintain tolerance, respectively. Since the discovery of two prototypic T helper cells, Th1 and Th2, additional phenotypic and functional distinct subsets have been described ranging from Th17, Th22, Th9, and T follicular helper cells. The same holds true for regulatory T cells that represent a family with functionally distinct subsets characterized by co-expression of the transcription factors T-bet, Gata3, or RORγt. Here, we summarize the current knowledge on differentiation and function of T helper and regulatory T cell subsets and discuss their lineage stability versus plasticity towards other subsets. In addition, we highlight the direct and indirect contribution of each subset to the pathology of allergies and indicate novel therapies for specific targeting the effector functions of T helper and regulatory T cells.

Two Sides of the Coin: Mast Cells as a Key Regulator of Allergy and Acute/Chronic Inflammation

It is well known that mast cells (MCs) initiate type I allergic reactions and inflammation in a quick response to the various stimulants, including—but not limited to—allergens, pathogen-associated molecular patterns (PAMPs), and damage-associated molecular patterns (DAMPs). MCs highly express receptors of these ligands and proteases (e.g., tryptase, chymase) and cytokines (TNF), and other granular components (e.g., histamine and serotonin) and aggravate the allergic reaction and inflammation. On the other hand, accumulated evidence has revealed that MCs also possess immune-regulatory functions, suppressing chronic inflammation and allergic reactions on some occasions. IL-2 and IL-10 released from MCs inhibit excessive immune responses. Recently, it has been revealed that allergen immunotherapy modulates the function of MCs from their allergic function to their regulatory function to suppress allergic reactions. This evidence suggests the possibility that manipulation of MCs functions will result in a novel approach to the treatment of various MCs-mediated diseases.

DNAM-1 regulates Foxp3 expression in regulatory T cells by interfering with TIGIT under inflammatory conditions

Regulatory T (Treg) cells that express forkhead box P3 (Foxp3) are pivotal for immune tolerance. Although inflammatory mediators cause Foxp3 instability and Treg cell dysfunction, their regulatory mechanisms remain incompletely understood. Here, we show that the transfer of Treg cells deficient in the activating immunoreceptor DNAM-1 ameliorated the development of graft-versus-host disease better than did wild-type Treg cells. We found that DNAM-1 competes with T cell immunoreceptor with Ig and ITIM domains (TIGIT) in binding to their common ligand CD155 and therefore regulates TIGIT signaling to down-regulate Treg cell function without DNAM-1-mediated intracellular signaling. DNAM-1 deficiency augments TIGIT signaling; this subsequently inhibits activation of the protein kinase B-mammalian target of rapamycin complex 1 pathway, resulting in the maintenance of Foxp3 expression and Treg cell function under inflammatory conditions. These findings demonstrate that DNAM-1 regulates Treg cell function via TIGIT signaling and thus, it is a potential molecular target for augmenting Treg function in inflammatory diseases.

Mast Cells and Skin and Breast Cancers: A Complicated and Microenvironment-Dependent Role

Mast cells are important sentinel cells in host defense against infection and major effector cells in allergic disease. The role of these cells in cancer settings has been widely debated. The diverse range of mast cell functions in both immunity and tissue remodeling events, such as angiogenesis, provides multiple opportunities for mast cells to modify the tumor microenvironment. In this review, we consider both skin and breast cancer settings to address the controversy surrounding the importance of mast cells in the host response to tumors. We specifically address the key mediators produced by mast cells which impact tumor development. The role of environmental challenges in modifying mast cell responses and opportunities to modify mast cell responses to enhance anti-tumor immunity are also considered. While the mast cell's role in many cancer contexts is complicated and poorly understood, the activities of these tissue resident and radioresistant cells can provide important opportunities to enhance anti-cancer responses and limit cancer development.

Bidirectional communication between mast cells and the gut-brain axis in neurodegenerative diseases: Avenues for therapeutic intervention

Although the global incidence of neurodegenerative diseases has been steadily increasing, especially in adults, there are no effective therapeutic interventions. Neurodegeneration is a heterogeneous group of disorders that is characterized by the activation of immune cells in the central nervous system (CNS) (e.g., mast cells and microglia) and subsequent neuroinflammation. Mast cells are found in the brain and the gastrointestinal tract and play a role in "tuning" neuroimmune responses. The complex bidirectional communication between mast cells and gut microbiota coordinates various dynamic neuro-cellular responses, which propagates neuronal impulses from the gastrointestinal tract into the CNS. Numerous inflammatory mediators from degranulated mast cells alter intestinal gut permeability and disrupt blood-brain barrier, which results in the promotion of neuroinflammatory processes leading to neurological disorders, thereby offsetting the balance in immune-surveillance. Emerging evidence supports the hypothesis that gut-microbiota exert a pivotal role in inflammatory signaling through the activation of immune and inflammatory cells. Communication between inflammatory cytokines and neurocircuits via the gut-brain axis (GBA) affects behavioral responses, activates mast cells and microglia that causes neuroinflammation, which is associated with neurological diseases. In this comprehensive review, we focus on what is currently known about mast cells and the gut-brain axis relationship, and how this relationship is connected to neurodegenerative diseases. We hope that further elucidating the bidirectional communication between mast cells and the GBA will not only stimulate future research on neurodegenerative diseases but will also identify new opportunities for therapeutic interventions.

Toward an understanding of regulatory T cells in COVID-19: A systematic review

A more detailed understanding of Treg cells in COVID-19 infection will broaden our knowledge of the COVID-19 immunopathology and give us more insight into the curative immune-based strategies. We systematically searched electronic databases (PubMed, Google Scholar, EMBASE) and identified 18 eligible studies. Despite the inconsistencies between the results, we observed a trend toward decreasing Treg levels in severe COVID-19 patients. This finding underlines the hypothesis that Tregs play a role in the pathogenesis of COVID-19. Further studies on Tregs' functional aspects are necessary to illustrate Tregs' potential role in COVID-19 disease.

IgE and mast cells: The endogenous adjuvant

Mast cells and IgE are most familiar as the effectors of type I hypersensitivity reactions including anaphylaxis. It is becoming clear however that this pair has important immunomodulatory effects on innate and adaptive cells of the immune system. In this purview, they act as endogenous adjuvants to ignite evolving immune responses, promote the transition of allergic disease into chronic illness and disrupt the development of active mechanisms of tolerance to ingested foods. Suppression of IgE-mediated mast cell activation can be exerted by molecules targeting IgE, FcɛRI or signaling kinases including Syk, or by IgG antibodies acting via inhibitory Fcγ receptors. In 2015 we reviewed the evidence for the adjuvant functions of mast cells. This update includes the original text, incorporates some important developments in the field over the past five years and discusses how interventions targeting these pathways might have promise in the development of strategies to treat allergic disease.