CD4+CD25+ T cells protect against experimentally induced asthma and alter pulmonary dendritic cell phenotype and function

Control of Asthma and Allergy by Regulatory T Cells

BACKGROUND

Epithelial barriers, such as the lungs and skin, face the challenge of providing the tissues' physiological function and maintaining tolerance to the commensal microbiome and innocuous environmental factors while defending the host against infectious microbes. Asthma and allergic diseases can result from maladaptive immune responses, resulting in exaggerated and persistent type 2 immunity and tissue inflammation.

SUMMARY

Among the diverse populations of tissue immune cells, CD4+ regulatory T cells (Treg cells) are central to controlling immune responses and inflammation and restoring tissue homeostasis. Humans and mice that are deficient in Treg cells experience extensive inflammation in their mucosal organs and skin. During past decades, major progress has been made toward understanding the immunobiology of Treg cells and the molecular and cellular mechanisms that control their differentiation and function. It is now clear that Treg cells are not a single cell type and that they demonstrate diversity and plasticity depending on their differentiation stages and tissue environment. They could also take on a proinflammatory phenotype in certain conditions.

KEY MESSAGES

Treg cells perform distinct functions, including the induction of immune tolerance, suppression of inflammation, and promotion of tissue repair. Subsets of Treg cells in mucosal tissues are regulated by their differentiation stage and tissue inflammatory milieu. Treg cell dysfunction likely plays roles in persistent immune responses and tissue inflammation in asthma and allergic diseases.

The role of deacetylase SIRT1 in allergic diseases

The silent information regulator sirtuin 1 (SIRT1) protein is an NAD+-dependent class-III lysine deacetylase that serves as an important post-transcriptional modifier targeting lysine acetylation sites to mediate deacetylation modifications of histones and non-histone proteins. SIRT1 has been reported to be involved in several physiological or pathological processes such as aging, inflammation, immune responses, oxidative stress and allergic diseases. In this review, we summarized the regulatory roles of SIRT1 during allergic disorder progression. Furthermore, we highlight the therapeutic effects of targeting SIRT1 in allergic diseases.

Dimethyl fumarate alleviates allergic asthma by strengthening the Nrf2 signaling pathway in regulatory T cells

Allergic asthma is a widely prevalent inflammatory condition affecting people across the globe. T cells and their secretory cytokines are central to the pathogenesis of allergic asthma. Here, we have evaluated the anti-inflammatory impact of dimethyl fumarate (DMF) in allergic asthma with more focus on determining its effect on T cell responses in allergic asthma. By utilizing the ovalbumin (OVA)-induced allergic asthma model, we observed that DMF administration reduced the allergic asthma symptoms and IgE levels in the OVA-induced mice model. Histopathological analysis showed that DMF treatment in an OVA-induced animal model eased the inflammation in the nasal and bronchial tissues, with a particular decrease in the infiltration of immune cells. Additionally, RT-qPCR analysis exhibited that treatment of DMF in an OVA-induced model reduced the expression of inflammatory cytokine (IL4, IL13, and IL17) while augmenting anti-inflammatory IL10 and Foxp3 (forkhead box protein 3). Mechanistically, we found that DMF increased the expression of Foxp3 by exacerbating the expression of nuclear factor E2-related factor 2 (Nrf2), and the in-vitro activation of Foxp3+ Tregs leads to an escalated expression of Nrf2. Notably, CD4-specific Nrf2 deletion intensified the allergic asthma symptoms and reduced the in-vitro iTreg differentiation. Meanwhile, DMF failed to exert protective effects on OVA-induced allergic asthma in CD4-specific Nrf2 knock-out mice. Overall, our study illustrates that DMF enhances Nrf2 signaling in T cells to assist the differentiation of Tregs, which could improve the anti-inflammatory immune response in allergic asthma.

Allergic Sensitization Driving Immune Phenotyping and Disease Severity in a Mouse Model of Asthma

PURPOSE

Asthma is a frequent chronic inflammatory bronchial disease affecting more than 300 million patients worldwide, 70% of whom are secondary to allergy. The diversity of asthmatic endotypes contributes to their complexity. The inter-relationship between allergen and other exposure and the airway microbiome adds to the phenotypic diversity and defines the natural course of asthma. Here, we compared the mouse models of house dust mite (HDM)-induced allergic asthma. Allergic sensitization was performed via various routes and associated with outcomes.

METHODS

Mice were sensitized with HDM via the oral, nasal or percutaneous routes. Lung function, barrier integrity, immune response and microbiota composition were analyzed.

RESULTS

Severe impairment of respiratory function was observed in the mice sensitized by the nasal and cutaneous paths. It was associated with epithelial dysfunction characterized by an increased permeability secondary to junction protein disruption. Such sensitization paths induced a mixed eosinophilic and neutrophilic inflammatory response with high interleukin (IL)-17 airway secretion. In contrast, orally sensitized mice showed a mild impairment of respiratory function. Epithelial dysfunction was mild with increased mucus production, but preserved epithelial junctions. Regarding lung microbiota, sensitization provoked a significant loss of diversity. At the genus level, Cutibacterium, Acinetobacter, Streptococcus and Lactobacillus were found to be modulated according to the sensitization pathway. An increase in theanti-inflammatory microbiota metabolites was observed in the oral-sensitization group.

CONCLUSIONS

Our study highlights the strong impact of the sensitization route on the pathophysiology and the critical phenotypic diversity of allergic asthma in a mouse model.

How does cigarette smoking affect airway remodeling in asthmatics?

Asthma is a prevalent chronic airway inflammatory disease involving multiple cells, and the prolonged course of the disease can cause airway remodeling, resulting in irreversible or partial irreversible airflow limitation and persistent airway hyperresponsiveness (AHR) in asthmatics. Therefore, we must ascertain the factors that affect the occurrence and development of airway remodeling in asthmatics. Smokers are not uncommon in asthmatics. However, there is no systematic description of how smoking promotes airway remodeling in asthmatics. This narrative review summarizes the effects of smoking on airway remodeling in asthmatics, and the progress of the methods for evaluating airway remodeling.

Human matters in asthma: Considering the microbiome in pulmonary health

Microbial communities form an important symbiotic ecosystem within humans and have direct effects on health and well-being. Numerous exogenous factors including airborne triggers, diet, and drugs impact these established, but fragile communities across the human lifespan. Crosstalk between the mucosal microbiota and the immune system as well as the gut-lung axis have direct correlations to immune bias that may promote chronic diseases like asthma. Asthma initiation and pathogenesis are multifaceted and complex with input from genetic, epigenetic, and environmental components. In this review, we summarize and discuss the role of the airway microbiome in asthma, and how the environment, diet and therapeutics impact this low biomass community of microorganisms. We also focus this review on the pediatric and Black populations as high-risk groups requiring special attention, emphasizing that the whole patient must be considered during treatment. Although new culture-independent techniques have been developed and are more accessible to researchers, the exact contribution the airway microbiome makes in asthma pathogenesis is not well understood. Understanding how the airway microbiome, as a living entity in the respiratory tract, participates in lung immunity during the development and progression of asthma may lead to critical new treatments for asthma, including population-targeted interventions, or even more effective administration of currently available therapeutics.

Gold Nanoparticles Inhibit Steroid-Insensitive Asthma in Mice Preserving Histone Deacetylase 2 and NRF2 Pathways

Background: Gold nanoparticles (AuNPs) can inhibit pivotal pathological changes in experimental asthma, but their effect on steroid-insensitive asthma is unclear. The current study assessed the effectiveness of nebulized AuNPs in a murine model of glucocorticoid (GC)-resistant asthma. Methods: A/J mice were sensitized and subjected to intranasal instillations of ovalbumin (OVA) once a week for nine weeks. Two weeks after starting allergen stimulations, mice were subjected to Budesonide or AuNP nebulization 1 h before stimuli. Analyses were carried out 24 h after the last provocation. Results: We found that mice challenged with OVA had airway hyperreactivity, eosinophil, and neutrophil infiltrates in the lung, concomitantly with peribronchiolar fibrosis, mucus production, and pro-inflammatory cytokine generation compared to sham-challenged mice. These changes were inhibited in mice treated with AuNPs, but not Budesonide. In the GC-resistant asthmatic mice, oxidative stress was established, marked by a reduction in nuclear factor erythroid 2-related factor 2 (NRF2) levels and catalase activity, accompanied by elevated values of thiobarbituric acid reactive substances (TBARS), phosphoinositide 3-kinases δ (PI3Kδ) expression, as well as a reduction in the nuclear expression of histone deacetylase 2 (HDAC2) in the lung tissue, all of which sensitive to AuNPs but not Budesonide treatment. Conclusion: These findings suggest that AuNPs can improve GC-insensitive asthma by preserving HDAC2 and NRF2.

Anaphylatoxins spark the flame in early autoimmunity

The complement system (CS) is an ancient and highly conserved part of the innate immune system with important functions in immune defense. The multiple fragments bind to specific receptors on innate and adaptive immune cells, the activation of which translates the initial humoral innate immune response (IR) into cellular innate and adaptive immunity. Dysregulation of the CS has been associated with the development of several autoimmune disorders such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), ANCA-associated vasculitis, and autoimmune bullous dermatoses (AIBDs), where complement drives the inflammatory response in the effector phase. The role of the CS in autoimmunity is complex. On the one hand, complement deficiencies were identified as risk factors to develop autoimmune disorders. On the other hand, activation of complement can drive autoimmune responses. The anaphylatoxins C3a and C5a are potent mediators and regulators of inflammation during the effector phase of autoimmunity through engagement of specific anaphylatoxin receptors, i.e., C3aR, C5aR1, and C5aR2 either on or in immune cells. In addition to their role in innate IRs, anaphylatoxins regulate humoral and cellular adaptive IRs including B-cell and T-cell activation, differentiation, and survival. They regulate B- and T-lymphocyte responses either directly or indirectly through the activation of anaphylatoxin receptors via dendritic cells that modulate lymphocyte function. Here, we will briefly review our current understanding of the complex roles of anaphylatoxins in the regulation of immunologic tolerance and the early events driving autoimmunity and the implications of such regulation for therapeutic approaches that target the CS.

Investigation of the effect of IFN-γ/TNF-α-treated mesenchymal stem cells on Th9- and Treg cell-related parameters in a mouse model of ovalbumin-induced allergic asthma

OBJECTIVE

Th9- and regulatory T (Treg) cells exert pro- and anti-allergic activity, respectively. Mesenchymal stem cell (MSC)-related immunomodulatory impacts can be enhanced by inflammatory cytokines. Here, the modulatory effects of IFN-γ/TNF-α-induced MSCs on Th9- and Treg cell-related parameters were investigated using an asthma model.

METHODS

Allergic asthma was induced in BALB/c mice using sensitized and challenging with ovalbumin (OVA). The asthmatic groups were treated intraperitoneally with PBS, MSCs, IFN-γ-induced MSCs, TNF-α-induced MSCs and "IFN-γ + TNF-α"-induced MSCs before the challenge phase. The mice were sacrificed 24 hours after challenge. The serum IL-9 and IL-35 levels, as well as gene expression of IL-9, PU.1, IL-35-EBI3 and FOXP3 in the lung tissues were assessed using ELISA and real time-PCR, respectively.

RESULTS

The differences of Th9 and Treg-related parameters were not significant between untreated asthmatic mice and those treated with non-induced MSCs. In comparison with untreated asthmatic group, treatment with IFN-γ-induced MSCs significantly reduced serum IL-9 levels, reduced lung expression of IL-9 and PU.1, while increasing serum IL-35 levels as well as lung expression of FOXP3; treatment with TNF-α-induced MSCs significantly reduced serum IL-9 levels as well as lung expression of IL-9, and treatment with "IFN-γ + TNF-α"-induced MSCs significantly modulated all investigated Th9 and Treg-related parameters. In comparison to mice treated with non-induced MSCs, serum IL-9 levels were remarkably decreased in mice treated with IFN-γ-induced and "IFN-γ + TNF-α"-induced MSCs.

CONCLUSIONS

IFN-γ-and "IFN-γ + TNF-α" treated MSCs exerted almost comparable impacts, but were more efficient than TNF-α-exposed MSCs. Thus, IFN-γ alone can be sufficient to promote immunomodulatory effects of MSCs.

Mucosal viral infection induces a regulatory T cell activation phenotype distinct from tissue residency in mouse and human tissues

Regulatory T cells (Tregs) mediate immune homeostasis, yet also facilitate nuanced immune responses during infection, balancing pathogen control while limiting host inflammation. Recent studies have identified Treg populations in non-lymphoid tissues that are phenotypically distinct from Tregs in lymphoid tissues (LT), including performance of location-dependent roles. Mucosal tissues serve as critical barriers to microbes while performing unique physiologic functions, so we sought to identify distinct phenotypical and functional aspects of mucosal Tregs in the female reproductive tract. In healthy human and mouse vaginal mucosa, we found that Tregs are highly activated compared to blood or LT Tregs. To determine if this phenotype reflects acute activation or a general signature of vaginal tract (VT)-residency, we infected mice with HSV-2 to discover that VT Tregs express granzyme-B (GzmB) and acquire a VT Treg signature distinct from baseline. To determine the mechanisms that drive GzmB expression, we performed ex vivo assays to reveal that a combination of type-I interferons and interleukin-2 is sufficient for GzmB expression. Together, we highlight that VT Tregs are activated at steady state and become further activated in response to infection; thus, they may exert robust control of local immune responses, which could have implications for mucosal vaccine design.

Acteoside exerts immunomodulatory effects on dendritic cells via aryl hydrocarbon receptor activation and ameliorates Th2-mediated allergic asthma by inducing Foxp3+ regulatory T cells

Dendritic cells (DCs) are professional antigen-presenting cells that play a key role in directing T-cell responses and are involved in the pathogenesis of allergic asthma. Acteoside, an active phenylethanoid glycoside, is widely distributed in many medicinal plants. Herein, we explored the immunomodulatory effects of acteoside on bone marrow-derived DCs in vitro, and further investigated the immunosuppressive ability of acteoside to manipulate T helper type 2 (Th2)-mediated allergic asthma in mice. Following lipopolysaccharide activation, 50 μM of acteoside significantly reduced the production of proinflammatory mediators, including interleukin (IL)-12 and tumor necrosis factor (TNF)-α, whereas it enhanced secretion of the anti-inflammatory cytokine, IL-10, by DCs. However, these effects of acteoside on DCs were reversed by pretreatment with CH223191, an aryl hydrocarbon receptor (AhR) antagonist. Additionally, coculture of acteoside-treated DCs with CD4⁺ T cells promoted the generation of forkhead box P3-positive (Foxp3⁺) regulatory T cells (Tregs) via AhR activation. Using a murine asthma model, our results demonstrated that oral administration of 50 mg/kg of acteoside decreased levels of Th2-type cytokines, such as IL-4, IL-5, and IL-13, whereas the level of IL-10 and the frequency of CD4⁺Foxp3⁺ Tregs were augmented. Moreover, acteoside treatment markedly inhibited the elevated serum level of ovalbumin-specific immunoglobulin E, attenuated the development of airway hyperresponsiveness, and reduced inflammatory cell counts in bronchoalveolar lavage fluid. Additionally, histological results reveled that acteoside ameliorated pulmonary inflammation in asthmatic mice. Taken together, these results indicated that acteoside exhibits immunomodulatory effects on DCs and plays an anti-inflammatory role in the treatment of allergic asthma.

Mucosal tissue regulatory T cells are integral in balancing immunity and tolerance at portals of antigen entry

Foxp3+ regulatory T cells (Tregs) are a subset of CD4+ T cells that exert suppressive control over other immune cells. Tregs are critical for preventing systemic autoimmunity and maintaining peripheral tolerance, and yet they also assist in orchestration of immunity to pathogenic insult, wherein they limit collateral immunopathology and assist in facilitating a fine balance between immune tolerance and effector activity. Tregs have been extensively studied in lymphoid tissues, and a growing body of work has characterized phenotypically distinct Tregs localized in various nonlymphoid tissue compartments. These tissue Tregs can perform location-specific, alternative functions, highlighting their dynamic, context-dependent roles. Tregs have also been identified in mucosal tissues where specialized physiological functions are paramount, including helping the host to respond appropriately to pathogenic versus innocuous antigens that are abundant at mucosal portals of antigen entry. As in other tissue Treg compartments, mucosal Tregs in the respiratory, gastrointestinal, and genitourinary tracts are distinct from circulating counterparts and can carry out mucosa-specific functions as well as classic suppressive functions that are the hallmark of Tregs. In this review, we summarize current knowledge regarding mucosal Tregs in both health and disease.

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.

Role of CD4+CD25+FOXP3+ TReg cells on tumor immunity

Not all T cells are effector cells of the anti-tumor immune system. One of the subpopulations of CD4⁺ T cells that express CD25⁺ and the transcription factor FOXP3, known as Regulator T cells (T_Reg), plays an essential role in maintaining tolerance and immune homeostasis preventing autoimmune diseases, minimalize chronic inflammatory diseases by enlisting various immunoregulatory mechanisms. The balance between effector T cells (T_eff) and regulator T cells is crucial in determining the outcome of an immune response. Regarding tumors, activation or expansion of T_Reg cells reduces anti-tumor immunity. T_Reg cells inhibit the activation of CD4⁺ and CD8⁺ T cells and suppress anti-tumor activity in the tumor microenvironment. In addition, T_Reg cells also promote tumor angiogenesis both directly and indirectly to ensure oxygen and nutrient transport to the tumor. There is accumulating evidence showing a positive result that removing or suppressing T_Reg cells increases anti-tumor immune response. However, depletion of T_Reg cells will cause autoimmunity. One strategy to improve or restore tumor immunity is targeted therapy on the dominant effector T_Reg cells in tumor tissue. Various molecules such as CTLA-4, CD4, CD25, GITR, PD-1, OX40, ICOS are in clinical trials to assess their role in attenuating T_Reg cells' function.

Respiratory Viral and Bacterial Factors That Influence Early Childhood Asthma

Asthma is a chronic respiratory condition characterised by episodes of shortness of breath due to reduced airway flow. The disease is triggered by a hyperreactive immune response to innocuous allergens, leading to hyper inflammation, mucus production, changes in structural cells lining the airways, and airway hyperresponsiveness. Asthma, although present in adults, is considered as a childhood condition, with a total of about 6.2 million children aged 18 and below affected globally. There has been progress in understanding asthma heterogeneity in adults, which has led to better patient stratification and characterisation of multiple asthma endotypes with distinct, but overlapping inflammatory features. The asthma inflammatory profile in children is not well-defined and heterogeneity of the disease is less described. Although many factors such as genetics, food allergies, antibiotic usage, type of birth, and cigarette smoke exposure can influence asthma development particularly in children, respiratory infections are thought to be the major contributing factor in poor lung function and onset of the disease. In this review, we focus on viral and bacterial respiratory infections in the first 10 years of life that could influence development of asthma in children. We also review literature on inflammatory immune heterogeneity in asthmatic children and how this overlaps with early lung development, poor lung function and respiratory infections. Finally, we review animal studies that model early development of asthma and how these studies could inform future therapies and better understanding of this complex disease.

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.

G Protein-Coupled Receptor Kinase 2 (GRK2) Regulates T Cell Response in a Murine Model of House Dust Mite-Induced Asthma

G protein-coupled receptor kinase 2 (GRK2) is an adapter protein that modulates G protein-coupled receptor (GPCR) signaling. It also regulates the functions and activity of other intracellular proteins in many cell types. Accordingly, GRK2 is thought to contribute to disease progression by a variety of mechanisms related to its multifunctional roles. Indeed, GRK2 levels are enhanced in patient samples as well as in preclinical models of several diseases. We have previously shown that GRK2 regulates mast cell functions, and thereby contributes to exacerbated inflammation during allergic reactions. In the current study, we observed that GRK2 levels are enhanced in the lungs of human asthma patients and in mice sensitized to house dust mite extract (HDME) allergen. Consistent with these findings, interleukin (IL)-4 and IL-13 levels were reduced in the lungs of GRK2+/- mice in a HMDE mouse model of asthma. Because Th2 cells are the major source of these cytokines during asthma, we determined the role of GRK2 in regulating T cell-specific responses in our HMDE mouse model. We observed a significant reduction of airway hyperresponsiveness (AHR), lung eosinophil and lymphocyte counts, serum IgE, Th2 cytokines (IL-4 and IL-13), goblet cell hyperplasia and mucus production in mice that had reduced GRK2 expression specifically in T cells. Collectively, our studies reveal an important role for GRK2 in regulating T cell response during asthma pathogenesis and further elucidation of the mechanisms through which GRK2 modulates airway inflammation will lead to the development of new therapeutic strategies for asthma.

Type I Interferon Production of Plasmacytoid Dendritic Cells under Control

One of the most powerful and multifaceted cytokines produced by immune cells are type I interferons (IFNs), the basal secretion of which contributes to the maintenance of immune homeostasis, while their activation-induced production is essential to effective immune responses. Although, each cell is capable of producing type I IFNs, plasmacytoid dendritic cells (pDCs) possess a unique ability to rapidly produce large amounts of them. Importantly, type I IFNs have a prominent role in the pathomechanism of various pDC-associated diseases. Deficiency in type I IFN production increases the risk of more severe viral infections and the development of certain allergic reactions, and supports tumor resistance; nevertheless, its overproduction promotes autoimmune reactions. Therefore, the tight regulation of type I IFN responses of pDCs is essential to maintain an adequate level of immune response without causing adverse effects. Here, our goal was to summarize those endogenous factors that can influence the type I IFN responses of pDCs, and thus might serve as possible therapeutic targets in pDC-associated diseases. Furthermore, we briefly discuss the current therapeutic approaches targeting the pDC-type I IFN axis in viral infections, cancer, autoimmunity, and allergy, together with their limitations defined by the Janus-faced nature of pDC-derived type I IFNs.

Single-cell transcriptomic analysis of allergen-specific T cells in allergy and asthma

CD4⁺ T helper (T_H) cells and regulatory T (T_reg) cells that respond to common allergens play an important role in driving and dampening airway inflammation in patients with asthma. Until recently, direct, unbiased molecular analysis of allergen-reactive T_H and T_reg cells has not been possible. To better understand the diversity of these T cell subsets in allergy and asthma, we analyzed the single-cell transcriptome of ~50,000 house dust mite (HDM) allergen-reactive T_H cells and T_reg cells from asthmatics with HDM allergy and from three control groups: asthmatics without HDM allergy and nonasthmatics with and without HDM allergy. Our analyses show that HDM allergen-reactive T_H and T_reg cells are highly heterogeneous and certain subsets are quantitatively and qualitatively different in individuals with HDM-reactive asthma. The number of interleukin-9 (IL-9)-expressing HDM-reactive T_H cells is greater in asthmatics with HDM allergy compared with nonasthmatics with HDM allergy, and this IL-9-expressing T_H subset displays enhanced pathogenic properties. More HDM-reactive T_H and T_reg cells expressing the interferon response signature (T_HIFNR and T_regIFNR) are present in asthmatics without HDM allergy compared with those with HDM allergy. In cells from these subsets (T_HIFNR and T_regIFNR), expression of TNFSF10 was enriched; its product, tumor necrosis factor-related apoptosis-inducing ligand, dampens activation of T_H cells. These findings suggest that the T_HIFNR and T_regIFNR subsets may dampen allergic responses, which may help explain why only some people develop T_H2 responses to nearly ubiquitous allergens.

Metformin alleviates allergic airway inflammation and increases Treg cells in obese asthma

Obesity increases the morbidity and severity of asthma, with poor sensitivity to corticosteroid treatment. Metformin has potential effects on improving asthma airway inflammation. Regulatory T cells (Tregs) play a key role in suppressing the immunoreaction to allergens. We built an obese asthmatic mouse model by administering a high-fat diet (HFD) and ovalbumin (OVA) sensitization, with daily metformin treatment. We measured the body weight and airway inflammatory status by histological analysis, qRT-PCR, and ELISA. The percentage of Tregs was measured by flow cytometry. Obese asthmatic mice displayed more severe airway inflammation and more significant changes in inflammatory cytokines. Metformin reversed the obese situation and alleviated the airway inflammation and remodelling with increased Tregs and related transcript factors. The anti-inflammatory function of metformin may be mediated by increasing Tregs.

Resistant starch intake alleviates collagen-induced arthritis in mice by modulating gut microbiota and promoting concomitant propionate production

Gut dysbiosis precedes clinic symptoms in rheumatoid arthritis (RA) and has been implicated in the initiation and persistence of RA. The early treatment of RA is critical to better clinical outcome especially for joint destruction. Although dietary interventions have been reported to be beneficial for RA patients, it is unclear to whether diet-induced gut microbiome changes can be a preventive strategy to RA development. Here, we investigated the effect of a high fiber diet (HFD) rich with resistant starch (RS) on collagen-induced arthritis (CIA) and gut microbial composition in mice. RS-HFD significantly reduced arthritis severity and bone erosion in CIA mice. The therapeutic effects of RS-HFD were correlated with splenic regulatory T cell (Treg) expansion and serum interleukin-10 (IL-10) increase. The increased abundance of Lactobacillus and Lachnoclostridium genera concomitant with CIA were eliminated in CIA mice fed the RS-HFD diet. Notably, RS-HFD also led to a predominance of Bacteroidetes, and increased abundances of Lachnospiraceae_NK4A136_group and Bacteroidales_S24-7_group genera in CIA mice. Accompanied with the gut microbiome changes, serum levels of the short-chain fatty acid (SCFA) acetate, propionate and isobutyrate detected by GC-TOFMS were also increased in CIA mice fed RS-HFD. While, addition of β-acids from hops extract to the drinking water of mice fed RS-HFD significantly decreased serum propionate and completely eliminated RS-HFD-induced disease improvement, Treg cell increase and IL-10 production in CIA mice. Moreover, exogenous propionate added to drinking water replicated the protective role of RS-HFD in CIA including reduced bone damage. The direct effect of propionate on T cells in vitro was further explored as at least one mechanistic explanation for the dietary effects of microbial metabolites on immune regulation in experimental RA. Taken together, RS-HFD significantly reduced CIA and bone damage and altered gut microbial composition with concomitant increase in circulating propionate, indicating that RS-rich diet might be a promising therapy especially in the early stage of RA.

Regulatory T cells mediated immunomodulation during asthma: a therapeutic standpoint

Asthma is an inflammatory disease of the lung airway network, which is initiated and perpetuated by allergen-specific CD4⁺ T cells, IgE antibodies, and a massive release of Th2 cytokines. The most common clinical manifestations of asthma progression include airway inflammation, pathological airway tissue and microvascular remodeling, which leads to airway hyperresponsiveness (AHR), and reversible airway obstruction. In addition to inflammatory cells, a tiny population of Regulatory T cells (Tregs) control immune homeostasis, suppress allergic responses, and participate in the resolution of inflammation-associated tissue injuries. Preclinical and clinical studies have demonstrated a tremendous therapeutic potential of Tregs in allergic airway disease, which plays a crucial role in immunosuppression, and rejuvenation of inflamed airways. These findings supported to harness the immunotherapeutic potential of Tregs to suppress airway inflammation and airway microvascular reestablishment during the progression of the asthma disease. This review addresses the therapeutic impact of Tregs and how Treg mediated immunomodulation plays a vital role in subduing the development of airway inflammation, and associated airway remodeling during the onset of disease.

Dendritic Cells: Critical Regulators of Allergic Asthma

Allergic asthma is a chronic inflammatory disease of the airways characterized by airway hyperresponsiveness (AHR), chronic airway inflammation, and excessive T helper (Th) type 2 immune responses against harmless airborne allergens. Dendritic cells (DCs) represent the most potent antigen-presenting cells of the immune system that act as a bridge between innate and adaptive immunity. Pertinent to allergic asthma, distinct DC subsets are known to play a central role in initiating and maintaining allergen driven Th2 immune responses in the airways. Nevertheless, seminal studies have demonstrated that DCs can also restrain excessive asthmatic responses and thus contribute to the resolution of allergic airway inflammation and the maintenance of pulmonary tolerance. Notably, the transfer of tolerogenic DCs in vivo suppresses Th2 allergic responses and protects or even reverses established allergic airway inflammation. Thus, the identification of novel DC subsets that possess immunoregulatory properties and can efficiently control aberrant asthmatic responses is critical for the re-establishment of tolerance and the amelioration of the asthmatic disease phenotype.

The immunomodulatory potentials of interleukin-27 in airway allergies

Allergic airway disorders such as asthma and allergic rhinitis are mainly caused by inhaled allergen-induced improper activation and responses of immune and non-immune cells. One important response is the production of IL-27 by macrophages and dendritic cells (DCs) during the early stage of airway allergies. IL-27 exerts powerful modulatory influences on the cells of innate immunity [eg neutrophils, eosinophils, mast cells, monocytes, macrophages, dendritic cells (DCs), innate lymphoid cells (ILCs), natural killer (NK) cells and NKT cells)] and adaptive immunity (eg Th1, Th2, Th9, Th17, regulatory T, CD8⁺ cytotoxic T and B cells). The IL-27-mediated signalling pathways may be modulated to attenuate asthma and allergic rhinitis. In this review, a comprehensive discussion concerning the roles carried out by IL-27 in asthma and allergic rhinitis was provided, while evidences are presented favouring the use of IL-27 in the treatment of airway allergies.

Elevated Circulating CD4+CD25+CD127-/low Regulatory T Cells in Patients with Non-asthmatic Eosinophilic Bronchitis

PURPOSE

Non-asthmatic eosinophilic bronchitis (NAEB) is a common cause of chronic cough. It is characterized by sputum eosinophilia like asthma but lacks airway hyperresponsiveness. Regulatory T cells (Tregs) are recognized as immune suppressors and are involved in the pathogenesis of asthma. However, the relationship between Tregs and NAEB remains unknown. This study aimed to preliminarily explore the role of Tregs in NAEB by comparing circulating Tregs levels to asthma and healthy controls.

METHODS

Fractional exhaled nitric oxide (FeNO), spirometry with bronchial provocation test, sputum induction and blood routine test were performed in all subjects. Peripheral blood mononuclear cells were used to detect the Tregs (CD4⁺CD25⁺CD127^-/low) by flow cytometry. Relationship between the levels of circulating Tregs and clinical indexes was also observed.

RESULTS

A total of 15 patients with NAEB, 20 patients with asthma and 11 healthy controls were included. The absolute numbers of circulating Tregs in the NAEB group (49.8 ± 18.9 × 10³ cells/ml) and asthma group (53.3 ± 18.7 × 10³ cells/ml) were higher than that in healthy control group (32.7 ± 11.6 × 10³ cells/ml) (both P < 0.01). In total, the level of circulating Tregs showed positive correlation with FeNO (r = 0.30, P < 0.05).

CONCLUSION

Tregs may play a key role not only in asthmatic patients, but also in patients with NAEB, as reflected by the elevated Tregs in peripheral blood.

Regulatory T cells in solid organ transplantation

The induction of graft tolerance remains the holy grail of transplantation. This is important as chronic allograft dysfunction and the side effects of immunosuppression regimens place a major burden on the lives of transplant patients and their healthcare systems. This has mandated the need to understand the immunobiology of graft rejection and identify novel therapeutics. Regulatory T (Treg) cells play an important role in modulating pro-inflammatory microenvironments and maintaining tissue homeostasis. However, there are fundamental unanswered questions regarding Treg cell immunobiology. These cells are a heterogeneous entity with functionally diverse roles. Moreover, the adoption of novel deeper immunophenotyping and genomic sequencing technologies has identified this phenotype and function to be more complex than expected. Hence, a comprehensive understanding of Treg cell heterogeneity is needed to safely and effectively exploit their therapeutic potential. From a clinical perspective, the recent decade has seen different clinical teams commence and complete first-in-man clinical trials utilising Treg cells as an adoptive cellular therapy. In this review, we discuss these trials from a translational perspective with an important focus on safety. Finally, we identify crucial knowledge gaps for future study.

Allergen-Induced C5a/C5aR1 Axis Activation in Pulmonary CD11b+ cDCs Promotes Pulmonary Tolerance through Downregulation of CD40

Activation of the C5/C5a/C5a receptor 1 (C5aR1) axis during allergen sensitization protects from maladaptive T cell activation. To explore the underlying regulatory mechanisms, we analyzed the impact of C5aR1 activation on pulmonary CD11b⁺ conventional dendritic cells (cDCs) in the context of house-dust-mite (HDM) exposure. BALB/c mice were intratracheally immunized with an HDM/ovalbumin (OVA) mixture. After 24 h, we detected two CD11b⁺ cDC populations that could be distinguished on the basis of C5aR1 expression. C5aR1⁻ but not C5aR1⁺ cDCs strongly induced T cell proliferation of OVA-reactive transgenic CD4⁺ T cells after re-exposure to antigen in vitro. C5aR1⁻ cDCs expressed higher levels of MHC-II and CD40 than their C5aR1⁺ counterparts, which correlated directly with a higher frequency of interactions with cognate CD4⁺ T cells. Priming of OVA-specific T cells by C5aR1⁺ cDCs could be markedly increased by in vitro blockade of C5aR1 and this was associated with increased CD40 expression. Simultaneous blockade of C5aR1 and CD40L on C5aR1⁺ cDCs decreased T cell proliferation. Finally, pulsing with OVA-induced C5 production and its cleavage into C5a by both populations of CD11b⁺ cDCs. Thus, we propose a model in which allergen-induced autocrine C5a generation and subsequent C5aR1 activation in pulmonary CD11b⁺ cDCs promotes tolerance towards aeroallergens through downregulation of CD40.

Natural killer cells as participants in pathogenesis of rat experimental autoimmune encephalomyelitis (EAE): lessons from research on rats with distinct age and strain

Natural killer (NK) cells, influencing dendritic cell (DC)-mediated CD4+ lymphocyte priming in draining lymph nodes (dLNs) and controlling spinal cord (SC) infiltration with encephalitogenic CD4+T lymphocytes, modulate EAE (multiple sclerosis model). This study examined their putative contribution to age-related differences in EAE development in Dark Agouti (DA) (exhibiting age-related decrease in EAE susceptibility) and Albino Oxford (AO) (becoming susceptible to EAE with aging) rats. Aging increased NK cell number in dLNs from rats of both strains. In AO rats, but not in DA ones, it also increased the numbers of IFN-γ-producing NK cells (important for DC activation) and activated/matured DCs, thereby increasing activated/matured DC/conventional Foxp3-CD4+ cell ratio and activated CD25+Foxp3-CD4+ cell number. Aging in DA rats diminished activated/matured DC/conventional Foxp3-CD4+ cell ratio and activated Foxp3-CD4+ cell number. However, MBP-stimulated CD4+ cell proliferation did not differ in dLN cell cultures from young and aged AO rats (as more favorable activated/matured DC/Foxp3-CD4+ cell ratio was abrogated by lower intrinsic CD4+ cell proliferative capacity and a greater regulatory CD25+Foxp3+CD4+ lymphocyte frequency), but was lower in those from aged compared with young DA rats. At SC level, aging shifted Foxp3-CD4+/cytotoxic CX3CR1+ NK cell ratio towards the former in AO rats, so it was less favorable in aged AO rats exhibiting prolonged neurological deficit compared with their DA counterparts. The study showed strain and age differences in number of IFN-γ-producing NK cells in EAE rat dLNs, and suggested that their pathogenetic relevance depends on frequency and/or activity of other cells involved in CD4+ T cell (auto)immune response.

Vaccine Potential of Mycobacterial Antigens against Asthma

Asthma is a cause of substantial burden of disease in the world, including both premature deaths and reduced quality of life. A leading hypothesis to explain the worldwide increase of asthma is the "hygiene hypothesis," which suggests that the increase in the prevalence of asthma is due to the reduction in exposure to infections/microbial antigens. In allergic asthma, the most common type of asthma, antigen-specific T helper (Th)2 and Th17 cells and their cytokines are primary mediators of the pathological consequences. In contrast, Th1 and T regulatory (Treg) cells and their cytokines play a protective role. This article aims to review the information on the effect of mycobacteria and their antigens in modulating Th2/Th17 responses towards Th1/Treg responses and protection against asthma in humans and animal models.

Dendritic cells treated with a prostaglandin I2 analog, iloprost, promote antigen-specific regulatory T cell differentiation in mice

Iloprost, a stable prostaglandin I₂ (PGI₂) analog, can inhibit allergic inflammation in an ovalbumin (OVA)-induced asthma model via inhibition of airway dendritic cell (DC) function. However, the underlying mechanism of PGI₂ signaling-mediated immunosuppression remains unclear. This study explored whether iloprost-treated DCs can suppress inflammation by promoting antigen-specific regulatory T cell (Treg) differentiation through PGI₂-G-protein-coupled receptor (IP). We established an allergic lung inflammation model using a hydrogel biomaterial delivery system and observed that iloprost significantly suppressed OVA-induced Th2 lung inflammation and increased the frequency of OVA-specific Tregs in vivo. We further observed that iloprost-treated DCs displayed tolerogenic characteristics, including low inflammatory cytokine (IL-12, TNF-α, IL-6, IL-23) expression levels, high anti-inflammatory cytokine (IL-10) production, and a semimature phenotype. In addition, iloprost-treated DCs increased OVA-specific CD4⁺Foxp3⁺ T cell differentiation from naïve T cells in an IP-dependent pathway in vitro and in vivo. Blocking experiments showed that iloprost-treated DCs promoted Treg differentiation, at least in part, through programmed death ligand 1 (PD-L1), whereas iloprost-induced PD-L1 expression in DCs was through the IP receptor. Furthermore, iloprost treatment suppressed DC-mediated airway inflammation and increased the frequency of OVA-specific Tregs through PD-L1 in vivo. Taken together, these results show that PGI₂-IP signaling mediated by iloprost in DCs may lead to immune tolerance, suggesting that the PGI₂ analog has the potential to be applied therapeutically for tolerogenic DC immunotherapy in autoimmune diseases or allergic asthma.

Chimeric antigen receptor -T cell therapy: Applications and challenges in treatment of allergy and asthma

Despite the current advancements, cancer treatment approaches have limitations restricting their cure rate. Immunotherapy techniques are among novel and promising cancer therapeutic approaches. Therapeutic antibodies and adoptive cell therapy (ACT) are the main branches of immunotherapy. T lymphocytes and genetically engineered cells are among important cells which can be used in ACT. This review has focused on recent advances in engineered cell-based immunotherapy based on T lymphocytes with chimeric antigen receptors (CARs). CARs are recombinant receptors expressing T cell signaling domains with or without co-stimulatory molecules. CAR-T cells are expanded ex vivo and re-infused to patients in order to improve their therapeutic efficacy. Nowadays, the beneficial function of CAR-T cell therapy has been indicated in various diseases including hematological malignancies, solid tumors, autoimmune diseases, and allergic diseases such as asthma. Furthermore, antigen-specific T regulatory cells (T_regs) and gene-edited T cells seem to be beneficial in controlling inflammation in allergic asthma. In fact, dysregulated function of T_regs is responsible for dominance of T helper 2 immune response and progression of allergic asthma. CAR-T_reg cells can also be designed and reproduced using iT_reg population to manage asthma. In addition, universal CAR-T cells can be modified to selectively target multiple antigens. The fourth generation CAR-T cells (i.e. TRUCK cells) represent novel strategies to cure asthma and allergic diseases as well. Despite the advantages of CAR-T cells, their applications can be associated with some unwanted reactions such as cytokine storm, anaphylaxis, neurotoxicity, etc. For clinical application, there is a need to prevent and manage these complications by optimizing ACT protocols.

Regulatory T Cells in Respiratory Health and Diseases

Respiratory diseases compromise the health of millions of people all over the world and are strongly linked to the immune dysfunction. CD4+FOXP3+ T regulatory cells, also known as Tregs, have a central role maintaining tissue homeostasis during immune responses. Their activity and clinical impact have been widely studied in different clinical conditions including autoimmune diseases, inflammatory conditions, and cancer, amongst others. Tregs express transcription factor forkhead box P3 (FOXP3), which allows regulation of the immune response through anti-inflammatory cytokines such as IL-10 or transforming growth factor beta (TGF-β) and direct cell-to-cell interaction. Maintenance of immune tolerance is achieved via modulation of effector CD4+ T helper 1, 2 or 17 (Th1, Th2, Th17) cells by Tregs. This review highlights the recent progress in the understanding of Tregs in different disorders of the respiratory system.

Der p2‑A20 DNA vaccine attenuates allergic inflammation in mice with allergic rhinitis

Allergic rhinitis (AR) is a common disease that requires more convenient, safe and effective antigen-specific immunotherapies. The present study aimed to investigate the therapeutic effect of intranasal administration of a eukaryotic expression vector co-expressing Der p2 and A20 protein (pVAX1-Der p2-A20) on mice with allergic rhinitis. The pVAX1-Der p2-A20 vaccine was prepared and encapsulated into poly(L-lactide-co-glycolide) (PLGA) nanoparticles. An allergic rhinitis Balb/c mouse model was established through intraperitoneal sensitization with recombinant Der p2 and cholera toxin followed by intranasal challenge with recombinant Der p2. The treatment effect of the DNA vaccine on nasal allergic inflammation was evaluated, and serum IgE, sIgE, IgG and cytokine levels were determined by ELISA. The percentage of CD4⁺CD25⁺Foxp3⁺Tregs in the spleen was detected by flow cytometry. The DNA vaccine co-expressing Der p2 and A20 was successfully constructed and encapsulated into PLGA nanoparticles. Der p2-A20 DNA vaccine intranasal administration markedly ameliorated Der p2-induced nasal allergic inflammation. The serum Der p2-specific IgE, IL-4 and IL-13 expression levels were inhibited, while the Der p2-specific IgG1, IgG2a and IFN-γ expression levels in the serum and splenic CD4⁺CD25⁺Foxp3⁺Treg population were significantly increased after Der p2-A20 DNA vaccine treatment. These results indicated that the Der p2-A20 DNA vaccine alleviates nasal allergic inflammation and promotes splenic Treg population in mice with allergic rhinitis.

Phenotype-Specific Therapeutic Effect of Rhodiola wallichiana var. cholaensis Combined with Dexamethasone on Experimental Murine Asthma and Its Comprehensive Pharmacological Mechanism

The heterogeneity of asthma involves complex pathogenesis leading to confusion regarding the choice of therapeutic strategy. In the clinic, asthma is commonly classified as having either eosinophilic asthma (EA) or non-eosinophilic asthma (NEA) phenotypes. Microbiota colonizing in airways has been demonstrated to induce distinct phenotypes of asthma and the resistance to steroids. Rhodiola wallichiana var. cholaensis (RWC) has the potential to alleviate asthmatic inflammation according to recent studies, but its pharmacological mechanisms remain unclarified. In our study, murine asthmatic phenotypes were established and treated with RWC and/or dexamethasone (DEX). Combined treatment with RWC and DEX could improve spirometry and airway hyperresponsiveness (AHR) in asthmatic phenotypes, alleviate steroid resistance in NEA, and reduce the inflammatory infiltration of the both phenotypes. The combined treatment increased Th1, regulated the imbalance of Th2/Th1, and decreased the related cytokines in EA. As for NEA, the combined treatment reduced Th17 and promoted the accumulation of regulatory T cells (Tregs) in lung. A microbiome study based on 16S rDNA sequencing technique revealed the significantly changed structure of the lower airway microbiota after combined treatment in NEA, with 4 distinct genera and 2 species identified. OPLS-DA models of metabolomics analysis based on UPLC-Q/TOF-MS technique identified 34 differentiated metabolites and 8 perturbed metabolic pathways. A joint multiomics study predicted that the colonized microbiota in airways might be associated with susceptibility of asthma and steroid resistance, which involved systematic and pulmonary metabolic perturbation. In summary, the pharmacological network of RWC included the complicated interaction mechanisms of immune regulation, microbiota change, and metabolic perturbation.

Multi-Faceted Notch in Allergic Airway Inflammation

Notch is an evolutionarily conserved signaling family which iteratively exerts pleiotropic functions in cell fate decisions and various physiological processes, not only during embryonic development but also throughout adult life. In the context of the respiratory system, Notch has been shown to regulate ciliated versus secretory lineage differentiation of epithelial progenitor cells and coordinate morphogenesis of the developing lung. Reminiscent of its role in development, the Notch signaling pathway also plays a role in repair of lung injuries by regulation of stem cell activity, cell differentiation, cell proliferation and apoptosis. In addition to functions in embryonic development, cell and tissue renewal and various physiological processes, including glucose and lipid metabolism, Notch signaling has been demonstrated to regulate differentiation of literally almost all T-cell subsets, and impact on elicitation of inflammatory response and its outcome. We have investigated the role of Notch in allergic airway inflammation in both acute and chronic settings. In this mini-review, we will summarize our own work and recent advances on the role of Notch signaling in allergic airway inflammation, and discuss potential applications of the Notch signaling family in therapy for allergic airway diseases.

MicroRNA-181a and microRNA-155 are involved in the regulation of the differentiation and function of regulatory T cells in allergic rhinitis children

BACKGROUND

Regulatory T cells (Tregs) play central roles in limiting airway allergic inflammation and preventing inappropriate Th2 responses to environmental allergens. This study aims to evaluate the role of miR-181a and miR-155 in the regulation of the differentiation and function of Tregs through both in vivo and in vitro studies.

METHODS

The CD4⁺ T cells and Tregs were purified from peripheral blood mononuclear cells (PBMCs) in allergic rhinitis (AR) children, respectively. The miR-155/181a mimics and inhibitors were transfected into CD4⁺ T cells and Tregs. The differentiation and function of Tregs were evaluated by flow cytometry and enzyme-linked immunosorbent assay. AR mice models were established, and miR-155/181a mimics or inhibitors were injected through tail vein. The Treg percentage and function from mice were compared among different groups.

RESULTS

The miR-181a up-regulated the release of interleukin (IL)-10 and TGF-β, whereas the miR-155 promoted Treg differentiation in CD4⁺ T cells. Similarly, we also found that miR-155 promoted Treg proliferation directly through suppressor of cytokine signaling 1 (SOCS1) and sirtuin1 (SIRT1) signaling pathway, whereas miR-181a up-regulated mRNA expression of IL-10 and TGF-β through phosphatidylinositol 3-OH kinase (PI3K)/Akt pathway. We also found that miR-155/181a affect Treg percentage and function in mice model.

CONCLUSION

Our findings suggest that miR-181a and miR-155 were closely correlated with the proliferation and function of Tregs in AR, providing new potential treatment target.

Targeting the ICOS/ICOS-L pathway in a mouse model of established allergic asthma disrupts T follicular helper cell responses and ameliorates disease

Background

Allergic asthma is characterized by chronic inflammation and remodelling of the airways, associated with dysregulated type 2 immune responses and allergen‐specific IgE. T follicular helper cells (T_FH) are crucial in T‐dependent B‐cell responses and have been implicated in allergic airway disease (AAD). T_FH, unlike other CD4⁺ T cells, are uniquely reliant on continuous ICOS signalling to maintain their phenotype after T‐cell priming; therefore, disrupting this signal can impair T_FH responses. However, the contribution of T_FH to disease during chronic aero‐allergen exposure and the therapeutic potential of targeting these cells have not been evaluated.

Methods

To establish AAD, female BALB/c mice were repeatedly exposed to house dust mite or Alternaria alternata three times a week for up to 5 weeks. To examine the impact of T_FH on AAD, mice were allergen exposed for 5 weeks and co‐administered anti‐ICOS Ligand‐targeted antibodies, three times a week for the last 2 weeks.

Results

T_FH were first observed in the lung‐draining lymph nodes and with further exposure were also found locally within the lungs. T_FH accumulated with sustained allergen exposure, alongside germinal centre (GC) B cells. Blockade of ICOS signalling after AAD establishment successfully depleted T_FH but did not affect the differentiation of other CD4⁺ T‐cell subsets. This reduced GC responses, allergen‐specific IgE, inflammation, pulmonary IL‐13 and airway hyper‐responsiveness.

Conclusions

T_FH are crucial in the regulation of AAD and the ICOS/ICOS‐L pathway could represent a novel therapeutic target in allergic asthma.

IL-27 targets Foxp3+ Tregs to mediate antiinflammatory functions during experimental allergic airway inflammation

Foxp3+ CD4 Tregs are central regulators of inflammation, including allergic inflammation in the lung. There is increasing evidence that inflammatory factors undermine adequate Treg functions and homeostasis, resulting in prolonged and exacerbated inflammation. Therefore, identifying the factors is of the utmost important. IL-27 is an antiinflammatory cytokine implicated in immune regulation and tolerance. However, the cellular mechanisms underlying IL-27-mediated immune regulation in vivo remain largely unknown. Utilizing a cockroach antigen-induced allergic inflammation model in mice, we sought to test the roles of Tregs during IL-27-mediated regulation of allergic inflammation. Intranasally delivered IL-27 significantly reduced the development of airway inflammation. Unexpectedly, the IL-27-induced reduction occurred only in the presence of Tregs. Il27ra-/- and Treg-specific Il27ra-/- mice developed severe airway inflammation, and IL-27 treatment had little impact on diminishing the inflammatory responses. IL-27-induced treatment was restored following transfer of WT Tregs but not of Tregs deficient in Lag3, a molecule induced by IL-27 in Tregs. Finally, Tregs from asthmatic patients exhibited blunted STAT1 phosphorylation following IL-27 stimulation. Taken together, our results uncover that Tregs are the primary target cells of IL-27 in vivo to mediate its antiinflammatory functions, suggesting that altered IL-27 responsiveness in Tregs may underlie inadequate Treg functions and perpetuation of inflammation.

Decreased Treg-derived miR-181a and miR-155 correlated with reduced number and function of Treg cells in allergic rhinitis children

BACKGROUND

Regulatory cells (Tregs) have been proved to be deeply involved in allergic airway inflammation. This study aims to evaluate the expression of miRNA in children with AR and their association with Tregs as well as the severity of AR.

METHODS

Twenty-five AR children and 20 healthy children were enrolled in this study. The Treg-cell percentage and expression of IL-10 and TGF-β were detected by flow cytometry and enzyme-linked immunosorbent assay. The microRNA microarray analysis in purified Tregs was performed and differentially expressed microRNAs were confirmed by quantitative polymerase chain reaction (qPCR).

RESULTS

Children with AR had lower percentage of Tregs and expression of IL-10 and TGF-beta compared with control children. We found that significantly lower levels of miR-155 and miR-181a in Tregs from AR than healthy controls. Furthermore, intracellular miR-155 and miR-181a level were positively correlated with percentage of Tregs and expression of IL-10 and TGF-beta. Similarly, total nasal severity scores (TNSS) were found to be negatively correlated with miR-155 and miR-181a levels.

CONCLUSION

Decreased Treg-derived miR-181a and miR-155 were correlated with reduced number and function of Tregs in AR children. The intracellular miR-155 and miR-181a levels may serve as predictors of disease severity in childhood AR.

Regulatory T cells and asthma

Asthma is a chronic disease of airway inflammation due to excessive T helper cell type 2 (Th2) response. Present treatment based on inhalation of synthetic glucocorticoids can only control Th2-driven chronic eosinophilic inflammation, but cannot change the immune tolerance of the body to external allergens. Regulatory T cells (Tregs) are the main negative regulatory cells of the immune response. Tregs play a great role in regulating allergic, autoimmune, graft-versus-host responses, and other immune responses. In this review, we will discuss the classification and biological characteristics, the established immunomodulatory mechanisms, and the characteristics of induced differentiation of Tregs. We will also discuss the progress of Tregs in the field of asthma. We believe that further studies on the regulatory mechanisms of Tregs will provide better treatments and control strategies for asthma.

Combined administration of anti-IL-13 and anti-IL-17A at individually sub-therapeutic doses limits asthma-like symptoms in a mouse model of Th2/Th17 high asthma

BACKGROUND

Recent studies have demonstrated that Th2 responses have the ability to antagonize Th17 responses. In mouse models of allergic asthma, blockade of Th2-effector cytokines results in elaboration of Th17 responses and associated increases in pulmonary neutrophilia. While these can be controlled by simultaneous blockade of Th17-associated effector cytokines, clinical trials of anti-IL-17/IL-17RA blocking therapies have demonstrated increased of risk of bacterial and fungal infections. Identification of minimally effective doses of cytokine-blocking therapies with the goal of reducing the potential emergence of infection-related complications is a translationally relevant goal.

OBJECTIVE

In the current report, we examine whether combined blockade of IL-13 and IL-17A, at individually sub-therapeutic levels, can limit the development of allergic asthma while sparing expression of IL-17A-associated anti-microbial effectors.

METHODS

House dust mite was given intratracheally to A/J mice. Anti-IL-13 and anti-IL-17A antibodies were administered individually, or concomitantly at sub-therapeutic doses. Airway hyper-reactivity, lung inflammation, magnitude of Th2- and Th17-associated cytokine production and expression of IL-13- and IL-17A-induced genes in the lungs was assessed.

RESULTS

Initial dosing studies identified sub-therapeutic levels of IL-13 and IL-17A blocking mAbs that have a limited effect on asthma parameters and do not impair responses to microbial products or infection. Subsequent studies demonstrated that combined sub-therapeutic dosing with IL-13 and IL-17A blocking mAbs resulted in significant improvement in airway hyperresponsiveness (AHR) and expression of IL-13-induced gene expression. Importantly, these doses neither exacerbated nor inhibited production of Th17-associated cytokines, or IL-17A-associated gene expression.

CONCLUSION

This study suggests that combining blockade of individual Th2 and Th17 effector cytokines, even at individually sub-therapeutic levels, may be sufficient to limit disease development while preserving important anti-microbial pathways. Such a strategy may therefore have reduced potential for adverse events associated with blockade of these pathways.

Antigen-specific regulatory T-cell responses against aeroantigens and their role in allergy

The mucosal immune system of the respiratory tract is specialized to continuously monitor the external environment and to protect against invading pathogens, while maintaining tolerance to innocuous inhaled particles. Allergies result from a loss of tolerance against harmless antigens characterized by formation of allergen-specific Th2 cells and IgE. Tolerance is often described as a balance between harmful Th2 cells and various types of protective "regulatory" T cells. However, the identity of the protective T cells in healthy vs. allergic individuals or following successful allergen-specific therapy is controversially discussed. Recent technological progress enabling the identification of antigen-specific effector and regulatory T cells has significantly contributed to our understanding of tolerance. Here we discuss the experimental evidence for the various tolerance mechanisms described. We try to integrate the partially contradictory data into a new model proposing different mechanism of tolerance depending on the quality and quantity of the antigens as well as the way of antigen exposure. Understanding the basis of tolerance is essential for the rational design of novel and more efficient immunotherapies.

Transplacental immune modulation with a bacterial-derived agent protects against allergic airway inflammation

Chronic allergic inflammatory diseases are a major cause of morbidity, with allergic asthma alone affecting over 300 million people worldwide. Epidemiological studies demonstrate that environmental stimuli are associated with either the promotion or prevention of disease. Major reductions in asthma prevalence are documented in European and US farming communities. Protection is associated with exposure of mothers during pregnancy to microbial breakdown products present in farm dusts and unprocessed foods and enhancement of innate immune competence in the children. We sought to develop a scientific rationale for progressing these findings toward clinical application for primary disease prevention. Treatment of pregnant mice with a defined, clinically approved immune modulator was shown to markedly reduce susceptibility of their offspring to development of the hallmark clinical features of allergic airway inflammatory disease. Mechanistically, offspring displayed enhanced dendritic cell-dependent airway mucosal immune surveillance function, which resulted in more efficient generation of mucosal-homing regulatory T cells in response to local inflammatory challenge. We provide evidence that the principal target for maternal treatment effects was the fetal dendritic cell progenitor compartment, equipping the offspring for accelerated functional maturation of the airway mucosal dendritic cell network following birth. These data provide proof of concept supporting the rationale for developing transplacental immune reprogramming approaches for primary disease prevention.

The levels of CD4+CD25+ regulatory T cells in patients with allergic rhinitis

Background: The involvement of CD4⁺CD25⁺ regulatory T cells (CD4⁺CD25⁺ T_Regs) in allergic diseases was reported previously. However, it remains unclear whether CD4⁺CD25⁺ T_Regs are involved in allergic rhinitis (AR). Methods: Fresh whole blood from 20 patients with AR and 16 healthy donors was used to investigate the frequency of CD4⁺CD25⁺ and CD4⁺CD25^hi Treg cells using flow cytometry. In addition, serum total IgE (IU/mL) levels were determined using enzyme-linked immunosorbent assays. Results: Patients with AR had fewer CD4⁺CD25⁺ Treg cells (2.80 ± 1.36% vs. 3.94 ± 0.97%, P < 0.01) and CD4⁺CD25^hi T_Regs (1.53 ± 0·62% vs. 2.00 ± 0.52%, P < 0.05) than control subjects. The number of CD4⁺CD25⁺ and CD4⁺CD25^hi T_Regs was correlated negatively with total immunoglobulin E levels (r = –0.79, P < 0.01 and r = –0.61, P < 0.01, respectively). Conclusion: Deficient regulatory T cells might play a role in the development of AR.

Intratracheal administration of adipose derived mesenchymal stem cells alleviates chronic asthma in a mouse model

BACKGROUND

Adipose-derived mesenchymal stem cell (ASCs) exerts immunomodulatory roles in asthma. However, the underlying mechanism remains unclear. The present study aimed to explore the effects and mechanisms of ASCs on chronic asthma using an ovalbumin (OVA)-sensitized asthmatic mouse model.

METHODS

Murine ASCs (mASCs) were isolated from male Balb/c mice and identified by the expression of surface markers using flow cytometry. The OVA-sensitized asthmatic mouse model was established and then animals were treated with the mASCs through intratracheal delivery. The therapy effects were assessed by measuring airway responsiveness, performing immuohistochemical analysis, and examining bronchoalveolar lavage fluid (BALF). Additionally, the expression of inflammatory cytokines and lgE was detected by CHIP and ELISA, respectively. The mRNA levels of serum indices were detected using qRT-PCR.

RESULTS

The mASCs grew by adherence with fibroblast-like morphology, and showed the positive expression of CD90, CD44, and CD29 as well as the negative expression of CD45 and CD34, indicating that the mASCs were successfully isolated. Administering mASCs to asthmatic model animals through intratracheal delivery reduced airway responsiveness, the number of lymphocytes (P < 0.01) and the expression of lgE (P < 0.01), IL-1β (P < 0.05), IL-4 (P < 0.001), and IL-17F (P < 0.001), as well as increased the serum levels of IL-10 and Foxp3, and the percentage of CD4 + CD25 + Foxp3+ Tregs in the spleen, and reduced the expression of IL-17 (P < 0.05) and RORγ.

CONCLUSIONS

Intratracheal administration of mASCs alleviated airway inflammation, improved airway remodeling, and relieved airway hyperresponsiveness in an OVA-sensitized asthma model, which might be associated with the restoration of Th1/Th2 cell balance by mASCs.

LPS inactivation by a host lipase allows lung epithelial cell sensitization for allergic asthma

This study provides strong evidence that intestinal commensal LPS desensitizes lung epithelial cells and therefore diminishes allergic responses to inhaled allergens. A host lipase, acyloxyacyl hydrolase (AOAH), prevents the desensitization by inactivating commensal LPS.

Allergic asthma is a chronic inflammatory disease primarily mediated by Th2 immune mechanisms. Numerous studies have suggested that early life exposure to lipopolysaccharide (LPS) is negatively associated with allergic asthma. One proposed mechanism invokes desensitization of lung epithelial cells by LPS. We report here that acyloxyacyl hydrolase (AOAH), a host lipase that degrades and inactivates LPS, renders mice more susceptible to house dust mite (HDM)–induced allergic asthma. Lung epithelial cells from Aoah^−/− mice are refractory to HDM stimulation, decreasing dendritic cell activation and Th2 responses. Antibiotic treatment that diminished commensal LPS-producing bacteria normalized Aoah^−/− responses to HDM, while giving LPS intrarectally ameliorated asthma. Aoah^−/− mouse feces, plasma, and lungs contained more bioactive LPS than did those of Aoah^+/+ mice. By inactivating commensal LPS, AOAH thus prevents desensitization of lung epithelial cells. An enzyme that prevents severe lung inflammation/injury in Gram-negative bacterial pneumonia has the seemingly paradoxical effect of predisposing to a Th2-mediated airway disease.

Tissue-Restricted Adaptive Type 2 Immunity Is Orchestrated by Expression of the Costimulatory Molecule OX40L on Group 2 Innate Lymphoid Cells

The local regulation of type 2 immunity relies on dialog between the epithelium and the innate and adaptive immune cells. Here we found that alarmin-induced expression of the co-stimulatory molecule OX40L on group 2 innate lymphoid cells (ILC2s) provided tissue-restricted T cell co-stimulation that was indispensable for Th2 and regulatory T (Treg) cell responses in the lung and adipose tissue. Interleukin (IL)-33 administration resulted in organ-specific surface expression of OX40L on ILC2s and the concomitant expansion of Th2 and Treg cells, which was abolished upon deletion of OX40L on ILC2s (Il7raCre/+Tnfsf4fl/fl mice). Moreover, Il7raCre/+Tnfsf4fl/fl mice failed to mount effective Th2 and Treg cell responses and corresponding adaptive type 2 pulmonary inflammation arising from Nippostrongylus brasiliensis infection or allergen exposure. Thus, the increased expression of OX40L in response to IL-33 acts as a licensing signal in the orchestration of tissue-specific adaptive type 2 immunity, without which this response fails to establish.