Increased airway T regulatory cells in asthmatic subjects

Investigating the T regulatory cells and Sirtuin-I serum level in immunotherapy treated house dust mite allergic asthma patients

OBJECTIVES

House dust mite aeroallergens are predominant triggers of frequent asthma attacks among adults and children. The intensity of asthma and immune reaction necessitates treatment alternatives based on adjusting chosen immunity biomarkers to control the exacerbation of symptoms and establish long-term immune tolerance. In this study, we selected CD4+CD25+Foxp3+ regulatory T cells (Tregs), FOXP3, and Sirtuin-1 as they are known to have a potential role in the immune reaction in different allergic diseases. We investigated their interplay during HDM allergic asthma and its respective immunotherapy.

METHODS

Eighty-four subjects were divided into 3 groups; healthy controls (CT), HDM asthma patients without immunotherapy (WOIT), and HDM asthma patients treated with subcutaneous immunotherapy for 6 months before recruitment (WIT). They were enrolled according to the pulmonary function, skin prick tests, and HDM-specific IgE. CD4+ CD25+ and CD4+ CD25+ FOXP3+hi T cells Cell percentages, FOXP3 gene expression, and Sirtuin-1 (Sirt1) serum level were analyzed.

RESULTS

We found that there is a significant difference between WOIT and WIT groups in the CD4+ CD25+ and CD4+ CD25+ FOXP3+hi T cell percentages. While there is no statistically significant difference between WOIT and WIT groups in FOXP3 level. On the controversy, the SIRT1 level in the CT group (4.53 ± 3.880) significantly decreased in the WOIT and WIT groups.

CONCLUSION

This study revealed that both CD4 CD25 and CD4 CD25 high FOXP3 cell percentages increased in the WIT group and declined in the WOIT group. While, FOXP3 gene expression increased in both groups. In addition, the Sirt1 serum level showed some improvement in WIT group after a serious drop in the WOIT group comparing with the CT group. The modulation of these biomarkers for the remission and control of allergic asthma can be a prognostic outcome of immunotherapy which needs to be confirmed by larger scale studies.

Endogenous inhibitory mechanisms in asthma

Endogenous inhibitory mechanisms promote resolution of inflammation, enhance tissue repair and integrity, and promote homeostasis in the lung. These mechanisms include steroid hormones, regulatory T cells, IL-10, prostaglandin E2, prostaglandin I2, lipoxins, resolvins, protectins, maresins, glucagon-like peptide-1 receptor, adrenomedullin, nitric oxide, and carbon monoxide. Here we review the most recent literature regarding these endogenous inhibitory mechanisms in asthma, which remain a promising target for the prevention and treatment of asthma.

A cell-level discriminative neural network model for diagnosis of blood cancers

MOTIVATION

Precise identification of cancer cells in patient samples is essential for accurate diagnosis and clinical monitoring but has been a significant challenge in machine learning approaches for cancer precision medicine. In most scenarios, training data are only available with disease annotation at the subject or sample level. Traditional approaches separate the classification process into multiple steps that are optimized independently. Recent methods either focus on predicting sample-level diagnosis without identifying individual pathologic cells or are less effective for identifying heterogeneous cancer cell phenotypes.

RESULTS

We developed a generalized end-to-end differentiable model, the Cell Scoring Neural Network (CSNN), which takes sample-level training data and predicts the diagnosis of the testing samples and the identity of the diagnostic cells in the sample, simultaneously. The cell-level density differences between samples are linked to the sample diagnosis, which allows the probabilities of individual cells being diagnostic to be calculated using backpropagation. We applied CSNN to two independent clinical flow cytometry datasets for leukemia diagnosis. In both qualitative and quantitative assessments, CSNN outperformed preexisting neural network modeling approaches for both cancer diagnosis and cell-level classification. Post hoc decision trees and 2D dot plots were generated for interpretation of the identified cancer cells, showing that the identified cell phenotypes match the cancer endotypes observed clinically in patient cohorts. Independent data clustering analysis confirmed the identified cancer cell populations.

AVAILABILITY AND IMPLEMENTATION

The source code of CSNN and datasets used in the experiments are publicly available on GitHub (http://github.com/erobl/csnn). Raw FCS files can be downloaded from FlowRepository (ID: FR-FCM-Z6YK).

Tissue-resident memory T cells and lung immunopathology

Rapid reaction to microbes invading mucosal tissues is key to protect the host against disease. Respiratory tissue-resident memory T (TRM ) cells provide superior immunity against pathogen infection and/or re-infection, due to their presence at the site of pathogen entry. However, there has been emerging evidence that exuberant TRM -cell responses contribute to the development of various chronic respiratory conditions including pulmonary sequelae post-acute viral infections. In this review, we have described the characteristics of respiratory TRM cells and processes underlying their development and maintenance. We have reviewed TRM -cell protective functions against various respiratory pathogens as well as their pathological activities in chronic lung conditions including post-viral pulmonary sequelae. Furthermore, we have discussed potential mechanisms regulating the pathological activity of TRM cells and proposed therapeutic strategies to alleviate TRM -cell-mediated lung immunopathology. We hope that this review provides insights toward the development of future vaccines or interventions that can harness the superior protective abilities of TRM cells, while minimizing the potential for immunopathology, a particularly important topic in the era of coronavirus disease 2019 (COVID-19) pandemic.

T helper 2 cells in asthma

Allergic asthma is among the most common immune-mediated diseases across the world, and type 2 immune responses are thought to be central to pathogenesis. The importance of T helper 2 (Th2) cells as central regulators of type 2 responses in asthma has, however, become less clear with the discovery of other potent innate sources of type 2 cytokines and innate mediators of inflammation such as the alarmins. This review provides an update of our current understanding of Th2 cells in human asthma, highlighting their many guises and functions in asthma, both pathogenic and regulatory, and how these are influenced by the tissue location and disease stage and severity. It also explores how biologics targeting type 2 immune pathways are impacting asthma, and how these have the potential to reveal hitherto underappreciated roles for Th2 cell in lung inflammation.

A cell-level discriminative neural network model for diagnosis of blood cancers

Motivation

Precise identification of cancer cells in patient samples is essential for accurate diagnosis and clinical monitoring but has been a significant challenge in machine learning approaches for cancer precision medicine. In most scenarios, training data are only available with disease annotation at the subject or sample level. Traditional approaches separate the classification process into multiple steps that are optimized independently. Recent methods either focus on predicting sample-level diagnosis without identifying individual pathologic cells or are less effective for identifying heterogeneous cancer cell phenotypes.

Results

We developed a generalized end-to-end differentiable model, the Cell Scoring Neural Network (CSNN), which takes the available sample-level training data and predicts both the diagnosis of the testing samples and the identity of the diagnostic cells in the sample, simultaneously. The cell-level density differences between samples are linked to the sample diagnosis, which allows the probabilities of individual cells being diagnostic to be calculated using backpropagation. We applied CSNN to two independent clinical flow cytometry datasets for leukemia diagnosis. In both qualitative and quantitative assessments, CSNN outperformed preexisting neural network modeling approaches for both cancer diagnosis and cell-level classification. Post hoc decision trees and 2D dot plots were generated for interpretation of the identified cancer cells, showing that the identified cell phenotypes match the cancer endotypes observed clinically in patient cohorts. Independent data clustering analysis confirmed the identified cancer cell populations.

Availability

The source code of CSNN and datasets used in the experiments are publicly available on GitHub and FlowRepository.

Contact

Edgar E. Robles: roblesee@uci.edu and Yu Qian: mqian@jcvi.org.

Supplementary information

Supplementary data are available on GitHub and at Bioinformatics online.

T-cell responses in asthma exacerbations

OBJECTIVE

Asthma is a chronic lung disease comprising multiple endotypes and characterized by periodic exacerbations. A diverse array of T cells has been found to contribute to all endotypes of asthma in pathogenic and regulatory roles. Here, we review the contributions of CD4+, CD8+, and unconventional T cells in allergic and nonallergic asthma.

DATA SOURCES

Review of published literature pertaining to conventional and unconventional T-cell types in asthma.

STUDY SELECTIONS

Recent peer-reviewed articles pertaining to T cells in asthma, with additional peer-reviewed studies for context.

RESULTS

Much research in asthma has focused on the roles of CD4+ TH cells. Roles for TH2 cells in promoting allergic asthma pathogenesis have been well-described, and the recent description of pathogenic TH2A cells provides additional insight into these responses. Other TH types, notably TH1 and TH17, have been linked to neutrophilic and steroid-resistant asthma phenotypes. Beyond CD4+ T cells, CD8+ Tc2 cells are also strongly associated with allergic asthma. An emerging area for study is unconventional T-cell types, including γδT, invariant natural killer T, and mucosal-associated invariant T cells. Although data in asthma remain limited for these cells, their ability to bridge innate and adaptive responses likely makes them key players in asthma. A number of asthma therapies target T-cell responses, and, although data are limited, they seem to modulate T-cell populations.

CONCLUSION

Given the diversity and heterogeneity of asthma and T-cell responses, there remain many rich avenues for research to better understand the pathogenesis of asthma. Despite the breadth of T cells in asthma, approved therapeutics remain limited to TH2 networks.

IL-36 Cytokines: Their Roles in Asthma and Potential as a Therapeutic

Interleukin (IL)-36 cytokines are members of the IL-1 superfamily, which consists of three agonists (IL-36α, IL-36β and IL-36γ) and an IL-36 receptor antagonist (IL-36Ra). IL-36 cytokines are crucial for immune and inflammatory responses. Abnormal levels of IL-36 cytokine expression are involved in the pathogenesis of inflammation, autoimmunity, allergy and cancer. The present study provides a summary of recent reports on IL-36 cytokines that participate in the pathogenesis of inflammatory diseases, and the potential mechanisms underlying their roles in asthma. Abnormal levels of IL-36 cytokines are associated with the pathogenesis of different types of asthma through the regulation of the functions of different types of cells. Considering the important role of IL-36 cytokines in asthma, these may become a potential therapeutic target for asthma treatment. However, existing evidence is insufficient to fully elucidate the specific mechanism underlying the action of IL-36 cytokines during the pathological process of asthma. The possible mechanisms and functions of IL-36 cytokines in different types of asthma require further studies.

Regulatory T Cells, a Viable Target Against Airway Allergic Inflammatory Responses in Asthma

Asthma is a multifactorial disorder characterized by the airway chronic inflammation, hyper-responsiveness (AHR), remodeling, and reversible obstruction. Although asthma is known as a heterogeneous group of diseases with various clinical manifestations, recent studies suggest that more than half of the clinical cases are ‘‘T helper type 2 (Th2)-high’’ type, whose pathogenesis is driven by Th2 responses to an inhaled allergen from the environmental exposures. The intensity and duration of inflammatory responses to inhaled allergens largely depend on the balance between effector and regulatory cells, but many questions regarding the mechanisms by which the relative magnitudes of these opposing forces are remained unanswered. Regulatory T cells (Tregs), which comprise diverse subtypes with suppressive function, have long been attracted extensive attention owing to their capability to limit the development and progression of allergic diseases. In this review we seek to update the recent advances that support an essential role for Tregs in the induction of allergen tolerance and attenuation of asthma progression once allergic airway inflammation established. We also discuss the current concepts about Treg induction and Treg-expressed mediators relevant to controlling asthma, and the therapies designed based on these novel insights against asthma in clinical settings.

[Immune system and allergies-An unholy alliance]

Various factors affect the maturation of the infantile immune system both prenatally and postnatally, including risk and protective factors from the environment, nutrition, genetics and epigenetics. The microbiome seems to play a substantial role. The complex interaction and regulation of all these factors is ultimately decisive for whether a child develops an allergy during the course of development of the immune system. The genetic components play a decisive role in the development of allergic diseases. The epigenetic regulation could represent a mechanism where environmental influences act upon the immune regulation in the emergence of allergic diseases. The main factors in the pathophysiology of allergic reactions are a dysregulation of various cells of the innate and acquired immune systems as well as their interaction. This review describes the role of various T helper cell types in allergic diseases. The incidence and duration of airway infections are clearly increased in allergic patients compared to nonallergic controls. In addition to functional aspects, the reason for the more frequent infections is an impairment of the immune defence by the allergy-related persisting inflammation of the mucous membranes. These mechanisms must be differentiated from a true immunodeficiency. Allergic rhinitis (AR) and bronchial asthma are nowadays no longer defined as separate diseases but as two forms of expression of an atopic entity with a similar pathology. Both diseases can be mediated by immunoglobulin E and be elicited by identical triggers. A bronchial hyperreactivity is detectable in the majority of patients with AR but without clinical asthma.

Immunological effects of adjuvanted low-dose allergoid allergen-specific immunotherapy in experimental murine house dust mite allergy

BACKGROUND

Native allergen extracts or chemically modified allergoids are routinely used to induce allergen tolerance in allergen-specific immunotherapy (AIT), although mechanistic side-by-side studies are rare. It is paramount to balance optimal dose and allergenicity to achieve efficacy warranting safety. AIT safety and efficacy could be addressed by allergen dose reduction and/or use of allergoids and immunostimulatory adjuvants, respectively. In this study, immunological effects of experimental house dust mite (HDM) AIT were investigated applying high-dose HDM extract and low-dose HDM allergoids with and without the adjuvants microcrystalline tyrosine (MCT) and monophosphoryl lipid A (MPL) in a murine model of HDM allergy.

METHODS

Cellular, humoral, and clinical effects of the different AIT strategies were assessed applying a new experimental AIT model of murine allergic asthma based on physiological, adjuvant-free intranasal sensitization followed by subcutaneous AIT.

RESULTS

While low-dose allergoid and high-dose extract AIT demonstrated comparable potency to suppress allergic airway inflammation and Th2-type cytokine secretion of lung-resident lymphocytes and draining lymph node cells, low-dose allergoid AIT was less effective in inducing a potentially protective IgG1 response. Combining low-dose allergoid AIT with MCT or MCT and dose-adjusted MPL promoted Th1-inducing mechanisms and robust B-cell activation counterbalancing the allergic Th2 immune response.

CONCLUSION

Low allergen doses induce cellular and humoral mechanisms counteracting Th2-driven inflammation by using allergoids and dose-adjusted adjuvants. In light of safety and efficacy improvement, future therapeutic approaches may use low-dose allergoid strategies to drive cellular tolerance and adjuvants to modulate humoral responses.

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.

Pulmonary-Resident Memory Lymphocytes: Pivotal Orchestrators of Local Immunity Against Respiratory Infections

There is increasing evidence that lung-resident memory T and B cells play a critical role in protecting against respiratory reinfection. With a unique transcriptional and phenotypic profile, resident memory lymphocytes are maintained in a quiescent state, constantly surveying the lung for microbial intruders. Upon reactivation with cognate antigen, these cells provide rapid effector function to enhance immunity and prevent infection. Immunization strategies designed to induce their formation, alongside novel techniques enabling their detection, have the potential to accelerate and transform vaccine development. Despite most data originating from murine studies, this review will discuss recent insights into the generation, maintenance and characterisation of pulmonary resident memory lymphocytes in the context of respiratory infection and vaccination using recent findings from human and non-human primate studies.

Reduced CCR6+IL-17A+Treg Cells in Blood and CCR6-Dependent Accumulation of IL-17A+Treg Cells in Lungs of Patients With Allergic Asthma

Human regulatory T (Treg) cells play a central role in controlling allergic inflammation in the airways. A reduced number of peripheral Treg cells and decreased suppressive function have been previously reported in the pathogenesis of allergic asthma. However, the characteristic role of specific Treg cell subsets and their mechanisms in the pathogenesis of allergic asthma remain unclear. In this study, we examined the proportion of different Treg cell subsets in both healthy subjects and patients with allergic asthma using flow cytometry and single-cell RNA sequencing. The migration function of the cells was compared using cell sorting and Transwell experiments. Furthermore, two allergen-challenged mouse models and a cell transfer experiment were used to examine the role of these Treg subsets. We found that the proportion of CD25⁺Foxp3⁺CD127^- Treg cells in the peripheral blood of patients with allergic asthma was lower than in those of healthy subjects. Furthermore, the circulating Treg cells expressed lower levels of CCR6 and IL-17 compared with healthy subjects. The chemokine from the airway mucosa, CCL20, was abundantly expressed, and Transwell experiments further proved that this chemokine promoted CCR6⁺ Treg cell migration in vitro. A mouse model induced by house dust mite (HDM) revealed that the number of CCR6⁺ Treg cells in the lung tissue increased remarkably. The incidence of allergic asthma may be related to an increase in Treg cells secreting IL-17 in the lung tissue. Recruited CCR6⁺ Treg cells are likely to differentiate into Th17-like cells under the Th17 environment present in the lungs. IL-17 derived from Th17-like cells could be associated with the pathology of allergic asthma by promoting Th17 responses, thereby favoring HDM-induced asthma exacerbations.

Association between interleukin-10 polymorphisms and CD4+CD25+FOXP3+ T cells in asthmatic children

OBJECTIVE

The aim of this study was to evaluate the association between possible functional interleukin-10 (IL-10) polymorphisms, IL-10 expression and regulatory T cells (Tregs) frequency, and/or asthma severity in a sample of children and adolescents.

METHODS

This is a nested case-control genetic association study. The study sample consisted of children and adolescents aged 8-14 from public schools. Four polymorphisms of the IL-10 gene (rs1518111, rs3024490, rs3024496, rs3024491) were genotyped in asthmatic subjects and controls using real-time PCR. Tregs cells and IL-10 were analyzed in peripheral blood mononuclear cells by flow cytometry. The severity of asthma was defined according to the Global Initiative for Asthma (GINA) guideline.

RESULTS

One hundred twenty-three asthmatic subjects and fifty-eight controls participated in the study. The single nucleotide polymorphism (SNP) rs3024491 (T allele) showed association with asthma severity, presenting a higher frequency in patients in the moderate asthma group. The T allele of variant rs3024491 also showed an association with reduced IL-10 levels (p=0.01) and with increased Tregs frequency (p=0.01). The other variants did not present consistent associations.

CONCLUSIONS

Our results suggest that moderate asthma is associated with a higher frequency of the T allele in the SNP rs3024491. In addition, the variant rs3024491 (TT) was associated with a reduction in IL-10 production and an increased percentage of Tregs cells, suggesting possible mechanisms that influence asthma severity.

Human Lung-Resident Macrophages Colocalize with and Provide Costimulation to PD1hi Tissue-Resident Memory T Cells

Rationale: Tissue-resident memory T cells (T_RM) play a critical role in the defense against inhaled pathogens. The isolation and study of human lung tissue-resident memory T cells and lung-resident macrophages (M_LR) are limited by experimental constraints. Objectives: To characterize the spatial and functional relationship between M_LR and human lung tissue-resident memory T cells using ex vivo lung perfusion (EVLP). Methods: T_RM and M_LR were isolated using EVLP and intraperfusate-labeled CD45 antibody. Cells isolated after 6 hours of EVLP were analyzed using spectral flow cytometry. Spatial relationships between CD3⁺ and CD68⁺ cells were explored with multiplexed immunohistochemistry. Functional relationships were determined by using coculture and T-cell-receptor complex signal transduction. Measurements and Main Results: Lungs from 8 research-consenting organ donors underwent EVLP for 6 hours. We show that human lung T_RM and M_LR colocalize within the human lung, preferentially around the airways. Furthermore, we found that human lung CD8⁺ T_RM are composed of two functionally distinct populations on the basis of PD1 (programed cell death receptor 1) and ZNF683 (HOBIT) protein expression. We show that M_LR provide costimulatory signaling to PD1^hi CD4⁺ and CD8⁺ lung T_RM,, augmenting the effector cytokine production and degranulation of T_RM. Conclusions: EVLP provides an innovative technique to study resident immune populations in humans. Human M_LR colocalize with and provide costimulation signaling to T_RM, augmenting their effector function.

Surface Phenotype Changes and Increased Response to Oxidative Stress in CD4+CD25high T Cells

Conversion of CD4+CD25+FOXP3+ T regulatory cells (Tregs) from the immature (CD45RA+) to mature (CD45RO+) phenotype has been shown during development and allergic reactions. The relative frequencies of these Treg phenotypes and their responses to oxidative stress during development and allergic inflammation were analysed in samples from paediatric and adult subjects. The FOXP3lowCD45RA+ population was dominant in early childhood, while the percentage of FOXP3highCD45RO+ cells began increasing in the first year of life. These phenotypic changes were observed in subjects with and without asthma. Further, there was a significant increase in phosphorylated ERK1/2 (pERK1/2) protein in hydrogen peroxide (H2O2)-treated CD4+CD25high cells in adults with asthma compared with those without asthma. Increased pERK1/2 levels corresponded with increased Ca2+ response to T cell receptor stimulation. mRNA expression of peroxiredoxins declined in Tregs from adults with asthma. Finally, CD4+CD25high cells from paediatric subjects were more sensitive to oxidative stress than those from adults in vitro. The differential Treg sensitivity to oxidative stress observed in children and adults was likely dependent on phenotypic CD45 isoform switching. Increased sensitivity of Treg cells from adults with asthma to H2O2 resulted from a reduction of peroxiredoxin-2, -3, -4 and increased pERK1/2 via impaired Ca2+ response in these cells.

Acute Severe Asthma in Adolescent and Adult Patients: Current Perspectives on Assessment and Management

Asthma is a chronic airway inflammatory disease that is associated with variable expiratory flow, variable respiratory symptoms, and exacerbations which sometimes require hospitalization or may be fatal. It is not only patients with severe and poorly controlled asthma that are at risk for an acute severe exacerbation, but this has also been observed in patients with otherwise mild or moderate asthma. This review discusses current aspects on the pathogenesis and pathophysiology of acute severe asthma exacerbations and provides the current perspectives on the management of acute severe asthma attacks in the emergency department and the intensive care unit.

IL-4 receptor α blockade prevents sensitization and alters acute and long-lasting effects of allergen-specific immunotherapy of murine allergic asthma

BACKGROUND

Allergen-specific immunotherapy (AIT) is the only causal treatment for allergy. However, success rates vary depending on the type of allergy and disease background of the patient. Hence, strategies targeting an increased therapeutic efficacy are urgently needed. Here, the effects of blockade of IL-4 and IL-13 signaling on different phases of AIT were addressed.

METHODS

The impact of the recombinantly produced IL-4 and IL-13 antagonist IL-4 mutein (IL-4M) on allergic sensitization and AIT outcome in experimental allergic asthma were analyzed in a murine model. The effects of IL-4M administration were assessed prior/during sensitization, immediately after AIT under allergen challenge, and two weeks post-treatment.

RESULTS

Intervention with IL-4M prior/during sensitization led to strong induction of IgG1, IgG2a, IgG2b, and IgG3, decrease of specific and total IgE, as well as of IL-5 in serum. Similar effects on the serum immunoglobulin levels were observed immediately after IL4M-supplemented AIT during allergen challenge. Additionally, IL4M markedly suppressed type-2 cytokine secretion of splenocytes beyond the effect of AIT alone. These effects were equaled to those of AIT alone two weeks post-treatment. Intriguingly, here, IL-4M induced a sustained decrease of Th2-biased Tregs (ST2⁺ FOXP3⁺ GATA3^intermediate ).

CONCLUSIONS

IL-4 and IL-13 blockade during experimental AIT demonstrates beneficial effects on immunological key parameters such as immunoglobulin and cytokine secretion immediately after AIT. Although two weeks later these effects were dropped to those of AIT alone, the number of potentially disease-triggering Th2-biased Tregs was further significantly decreased by IL-4M treatment. Hence, IL-4/IL13-targeting therapies prime the immune memory in therapy success-favoring manner.

[Reasons for the development of allergies in children]

Allergies are one of the most common chronic diseases in childhood, contributing to a tremendous medical and economical burden in health care systems of most industrialized countries. The development of allergies is dependent on a complex interaction of-among others-environmental factors, nutrition, genetic and epigenetic mechanisms as well as the microbiome. These diverse factors can influence early life immune regulation including innate and adaptive immune mechanisms in a complex fashion. In case of any Childhood allergies have increased significantly in past decades. In addition to environmental factors and nutrition, genetic and epigenetic mechanisms as well as the microbiome of children play an important role. Of relevance is the way in which these diverse factors influence early immune development of the innate and adaptive immune systems of children. Their complex regulation is decisive for whether or not a child develops an allergy that manifests in most cases as atopic dermatitis, bronchial asthma, or allergic rhino conjunctivitis, or whether a child develops an immune tolerance. These influences can begin prenatally, already setting the course for later immune system development and occurrence of disease.

Human lung tissue resident memory T cells in health and disease

The human lung contains a heterogeneous population of immune cells which mediate protective responses, maintain tissue homeostasis, but can also promote immunopathology in disease. The majority of T cells in the human lung are tissue resident memory T cells (T_RM) which have been shown in mouse models to provide vital roles in the protection against multiple respiratory pathogens, and contribute to heterosubtypic protection in the context of vaccination. In this review, we will discuss recent studies in humans identifying lung TRM, their role in maintaining tissue homeostasis, and emerging evidence implicating T_RM in anti-tumor immunity and immune surveillance as well as their potential for immunopathology in chronic airway inflammation.

Antiallergic Effect of Hizikia fusiformis in an Ovalbumin-Induced Allergic Rhinitis Mouse Model

Objectives

The extract of Hizikia fusiformis is known to exhibit anticancer, antiatopic and antioxidant activities. We aimed to investigate the extract of H. fusiformis on allergic rhinitis inflammation in a mouse model.

Methods

The 4-week-old BALB/c mice were randomly assigned into four groups: group A, control group (n=9); group B, allergic rhinitis group (n=10); group C (n=10) received 300 mg/kg of H. fusiformis during nasal challenging period; group D (n=10) received 600 mg/kg of H. fusiformis during general sensitization period and 300 mg/kg of H. fusiformis during nasal challenging period. Allergic inflammation was made with ovalbumin (OVA) and alum then challenged intranasally with OVA. H. fusiformis was intraperitoneally administered 3 hours before the OVA administration. Allergic symptom score and the levels of immunoglobulin G₁ (IgG₁), IgG_2a, OVA-specific IgE antibodies, levels of cytokines in the nasal mucosa and in spleen cell culture supernatant, such as tumor necrosis factor alpha (TNF-α), interleukin 4 (IL-4), IL-5, IL-13, and IL-10 were assessed. The percentage of regulatory T cell was analyzed by flow cytometry. Eosinophilic infiltration and goblet cell hyperplasia were also evaluated.

Results

H. fusiformis administered groups C and D showed significant inhibitory effects on nasal symptoms, IL-13 mRNA expression and eosinophil infiltration/goblet cell hyperplasia in the nasal tissue; OVA-specific IgE production in serum (P<0.05). In group D, H. fusiformis treatment downregulated IL-4, IL-5, IL-13, TNF-α, and IL-10 cytokine expression in splenocyte culture as well as significantly decreased IgG_2a, IgG₁ levels in serum compared with group B (P<0.05). However, the expressions of IL-5, interferon-γ and forkhead box P3 mRNA did not change in groups C and D.

Conclusion

H. fusiformis could induce antiallergic inflammation by suppressing the T-helper type 2 cytokine production (IL-13) locally and systemically, OVA-specific IgE formation, goblet cell hyperplasia, and eosinophilic infiltration in a mouse model of allergic rhinitis. Thus, H. fusiformis could be considered as a potential therapeutic agent in treating allergic rhinitis.

Glucocorticosteroids administration is associated with increased regulatory T cells in equine asthmatic lungs

Recurrent inflammation in severe equine asthma causes a remodeling of the airways leading to incompletely reversible airway obstruction. Despite the improvement of clinical signs and lung function with glucocorticoids (GC), inflammation, translated by an increased percentage of neutrophils, persists in the airways. Regulatory T cells (Treg) have been shown to have anti-inflammatory properties and play an important role in balancing the immune response by suppressing effector lymphocyte activity. However, interactions between Treg, neutrophils and glucocorticosteroids in vivo are unclear, particularly in asthma. Furthermore, the effects of GC on Treg in the airway of asthmatic horses have not been investigated. We hypothesized that horses with severe asthma display a decreased population of pulmonary Treg when compared to heathy controls, and that treatment with GC lead to an increased pulmonary Treg cell population only in affected horses. Using lung function measurements and flow cytometry with surface antigens CD4 and FoxP3, we investigated Treg in airway luminal cells obtained by bronchoalveolar lavage fluid (BALF) from 6 asthmatic horses in exacerbation of the disease and 6 aged-match controls, kept in the same environment, before and following a 2-week treatment with dexamethasone. Results showed that the number of Treg increases only in the lungs of asthmatic horses following GC therapy, despite continued presence of increased numbers of neutrophils. Our results support the complexity of the interaction between Treg, neutrophils and GC.

Lung-Infiltrating Foxp3+ Regulatory T Cells Are Quantitatively and Qualitatively Different during Eosinophilic and Neutrophilic Allergic Airway Inflammation but Essential To Control the Inflammation

Understanding functions of Foxp3⁺ regulatory T cells (Tregs) during allergic airway inflammation remains incomplete. In this study, we report that, during cockroach Ag-induced allergic airway inflammation, Foxp3⁺ Tregs are rapidly mobilized into the inflamed lung tissues. However, the level of Treg accumulation in the lung was different depending on the type of inflammation. During eosinophilic airway inflammation, ∼30% of lung-infiltrating CD4 T cells express Foxp3, indicative of Tregs. On the contrary, only ∼10% of infiltrating CD4 T cells express Foxp3 during neutrophilic airway inflammation. Despite the different accumulation, the lung inflammation and inflammatory T cell responses were aggravated following Treg depletion, regardless of the type of inflammation, suggesting regulatory roles for Tregs. Interestingly, however, the extent to which inflammatory responses are aggravated by Treg depletion was significantly greater during eosinophilic airway inflammation. Indeed, lung-infiltrating Tregs exhibit phenotypic and functional features associated with potent suppression. Our results demonstrate that Tregs are essential regulators of inflammation, regardless of the type of inflammation, although the mechanisms used by Tregs to control inflammation may be shaped by environmental cues available to them.

Chimeric Antigen Receptor-Redirected Regulatory T Cells Suppress Experimental Allergic Airway Inflammation, a Model of Asthma

Cellular therapy with chimeric antigen receptor (CAR)-redirected cytotoxic T cells has shown impressive efficacy in the treatment of hematologic malignancies. We explored a regulatory T cell (Treg)-based therapy in the treatment of allergic airway inflammation, a model for asthma, which is characterized by an airway hyper-reactivity (AHR) and a chronic, T helper-2 (Th2) cell-dominated immune response to allergen. To restore the immune balance in the lung, we redirected Tregs by a CAR toward lung epithelia in mice upon experimentally induced allergic asthma, closely mimicking the clinical situation. Adoptively transferred CAR Tregs accumulated in the lung and in tracheobronchial lymph nodes, reduced AHR and diminished eosinophilic airway inflammation, indicated by lower cell numbers in the bronchoalveolar lavage fluid and decreased cell infiltrates in the lung. CAR Treg cells furthermore prevented excessive pulmonary mucus production as well as increase in allergen-specific IgE and Th2 cytokine levels in exposed animals. CAR Tregs were more efficient in controlling asthma than non-modified Tregs, indicating the pivotal role of specific Treg cell activation in the affected organ. Data demonstrate that lung targeting CAR Treg cells ameliorate key features of experimental airway inflammation, paving the way for cell therapy of severe allergic asthma.

Regulatory T Cell and Forkhead Box Protein 3 as Modulators of Immune Homeostasis

The transcription factor forkhead box protein 3 (FOXP3) is an essential molecular marker of regulatory T cell (Treg) development in different microenvironments. Tregs are cells specialized in the suppression of inadequate immune responses and the maintenance of homeostatic tolerance. Studies have addressed and elucidated the role played by FOXP3 and Treg in countless autoimmune and infectious diseases as well as in more specific cases, such as cancer. Within this context, the present article reviews aspects of the immunoregulatory profile of FOXP3 and Treg in the management of immune homeostasis, including issues relating to pathology as well as immune tolerance.

Peripherally Generated Foxp3+ Regulatory T Cells Mediate the Immunomodulatory Effects of IVIg in Allergic Airways Disease

IVIg is widely used as an immunomodulatory therapy. We have recently demonstrated that IVIg protects against airway hyperresponsiveness (AHR) and inflammation in mouse models of allergic airways disease (AAD), associated with induction of Foxp3⁺ regulatory T cells (Treg). Using mice carrying a DTR/EGFP transgene under the control of the Foxp3 promoter (DEREG mice), we demonstrate in this study that IVIg generates a de novo population of peripheral Treg (pTreg) in the absence of endogenous Treg. IVIg-generated pTreg were sufficient for inhibition of OVA-induced AHR in an Ag-driven murine model of AAD. In the absence of endogenous Treg, IVIg failed to confer protection against AHR and airway inflammation. Adoptive transfer of purified IVIg-generated pTreg prior to Ag challenge effectively prevented airway inflammation and AHR in an Ag-specific manner. Microarray gene expression profiling of IVIg-generated pTreg revealed upregulation of genes associated with cell cycle, chromatin, cytoskeleton/motility, immunity, and apoptosis. These data demonstrate the importance of Treg in regulating AAD and show that IVIg-generated pTreg are necessary and sufficient for inhibition of allergen-induced AAD. The ability of IVIg to generate pure populations of highly Ag-specific pTreg represents a new avenue to study pTreg, the cross-talk between humoral and cellular immunity, and regulation of the inflammatory response to Ags.

Mechanisms Mediating Pediatric Severe Asthma and Potential Novel Therapies

Although a rare disease, severe therapy-resistant asthma in children is a cause of significant morbidity and results in utilization of approximately 50% of health-care resources for asthma. Improving control for children with severe asthma is, therefore, an urgent unmet clinical need. As a group, children with severe asthma have severe and multiple allergies, steroid resistant airway eosinophilia, and significant structural changes of the airway wall (airway remodeling). Omalizumab is currently the only add-on therapy that is licensed for use in children with severe asthma. However, limitations of its use include ineligibility for approximately one-third of patients because of serum IgE levels outside the recommended range and lack of clinical efficacy in a further one-third. Pediatric severe asthma is thus markedly heterogeneous, but our current understanding of the different mechanisms underpinning various phenotypes is very limited. We know that there are distinctions between the factors that drive pediatric and adult disease since pediatric disease develops in the context of a maturing immune system and during lung growth and development. This review summarizes the current data that give insight into the pathophysiology of pediatric severe asthma and will highlight potential targets for novel therapies. It is apparent that in order to identify novel treatments for pediatric severe asthma, the challenge of undertaking mechanistic studies using age appropriate experimental models and airway samples from children needs to be accepted to allow a targeted approach of personalized medicine to be achieved.

T regulatory cell phenotypes in peripheral blood and bronchoalveolar lavage from non-asthmatic and asthmatic subjects

BACKGROUND

An unresolved issue in T regulatory cells' cell biology is the lack of consensus on phenotypic markers that accurately define the natural Treg (nTreg) population.

OBJECTIVES

To examine nTreg frequency and functional capacity in healthy controls and their frequency in asthmatic subjects using three different phenotypic strategies. We hypothesized that phenotypically different nTreg are quantitatively and functionally different.

METHODS

Thirty-four healthy, non-asthmatic and 17 asthmatic subjects were studied. Three nTreg phenotypes were defined as follows: nTreg1 (CD4(+) CD25(+) Foxp3(+) ), nTreg2 (CD4(+) CD25(+) CD127(low) Foxp3(+) ), and nTreg3 (CD4(+) CD25(high) Foxp3(+) ). The flow cytometric determination of nTreg frequency in peripheral blood (PB) and bronchoalveolar lavage (BAL) was performed using fluorescently labelled antibodies. Peripheral blood nTreg functional capacity was assessed using a CFSE-based suppression assay.

RESULTS

There was a significantly lower frequency of PB nTreg3 compared to nTreg2 and nTreg1 (P < 0.05). Both nTreg2 and nTreg3 had a significantly greater suppressive capacity than nTreg1 at T responder (Tresp) to nTreg ratios of 16 : 1 up to 1 : 1 (P < 0.01). Asthmatics exhibited a significantly lower PB nTreg3 and nTreg1 frequency than healthy controls (P < 0.05). There were no differences between healthy controls and asthmatic subjects when comparing BAL nTreg frequency.

CONCLUSIONS AND CLINICAL RELEVANCE

Phenotypically different nTreg subsets are quantitatively and functionally different and are variably observed in asthma. The CD4(+) CD25(high) Foxp3(+) phenotype was the least frequent, but demonstrated the greatest suppression, and was significantly lower in PB of asthmatic subjects. Consequently, it is imperative that nTreg phenotypes be clearly defined and that the interpretation of their frequency and function be phenotype specific.

Decreased FOXP3 mRNA expression in children with atopic asthma and IgE-mediated food allergy

BACKGROUND

The role of T regulatory lymphocytes has been investigated in various allergic diseases. However, the precise relation between the phenotype and severity of allergic diseases and the changes in FOXP3 mRNA expression are not fully understood.

OBJECTIVE

To compare the expression of FOXP3 mRNA in children with asthma with and without concomitant food allergy (FA) with healthy children and children with only FA.

METHODS

The study included 82 children: 15 with atopic asthma and IgE-dependent FA, 27 with atopic asthma without FA, 20 with IgE-dependent FA without asthma, and 20 healthy children without atopy. Reverse transcription was performed using a commercially available High Capacity cDNA Archive Kit (Applied Biosystems, Carlsbad, California). Analysis was carried out with a 7900HT real-time polymerase chain reaction system (Applied Biosystems).

RESULTS

The average level of the FOXP3 gene expression in children with allergy was significantly lower compared with healthy children (2.2 ± 1.3 vs 4.2 ± 4.2; P = .014). The lowest mean level of FOXP3 mRNA expression (1.9 ± 1.6) was recorded in children with asthma and FA, and the highest level (4.2 ± 4.2) was recorded in healthy children without atopy (P = .036). A milder course of asthma or the degree of allergic reaction after a food challenge was associated with higher FOXP3 mRNA expression.

CONCLUSION

Significantly lower levels of FOXP3 gene expression, observed more commonly in children with asthma and IgE-dependent FA than in healthy controls, were associated with a more severe clinical course. Therefore, FOXP3 expression could serve as an indicator of severe asthma with concomitant atopic conditions such as IgE-dependent FA.

Elevated receptor for activated C kinase 1 expression is involved in intracellular Ca2+ influx and potentially associated with compromised regulatory T cell function in patients with asthma

BACKGROUND

Regulatory T cells (T(regs)) are activated during anergy in response to T cell receptor (TCR) activation and functional immune suppression. Anergy of paediatric T(regs) is partially dependent on intracellular calcium mobility; following TCR activation, T(regs) do not exhibit increased intracellular Ca(2+) concentration ([Ca(2+) ](i)).

OBJECTIVE

We determined whether [Ca(2+) ](i) in adult T(regs) defined their anergy, if intracellular Ca(2+) movement was linked to regulatory functions, whether [Ca(2+)](i) was indicative of asthma pathology, and the potential molecular mechanism responsible for Ca(2+) movement in T(regs).

METHODS

T(regs) were purified by the magnetic bead method, and their regulatory functions were assessed by monitoring carboxyfluorescein succinimidyl ester-labelled responder T cell proliferation. The Ca(2+) response of Fura-2-labelled cells was measured using a video image analysis system. To analyse the functions of T(regs) at the molecular level, we generated Jurkat Tet-On(®) clones with doxycycline (Dox)-induced forkhead box P3 (FOXP3) protein expression.

RESULTS

CD4(+) CD25(+) CD127(-/low) T(regs) from participants without asthma did not elicit Ca(2+) influx in response to TCR activation, exhibited little proliferation and suppressed proliferation of CD4(+) CD25(-) T cells. In contrast, under similar conditions, T(regs) from patients with asthma exhibited increased [Ca(2+)](i) and robust proliferation with partial loss of regulatory functions. FOXP3 protein levels in Tet-On(®) clones were high after both 2- and 5-day Dox treatment; however, 5-day cells were comparable with T(regs) from patients with asthma, whereas 2-day cells were similar to T(regs) from participants without asthma. Increasing [Ca(2+)](i) induced a high level of receptor for activated C kinase 1 (RACK1) expression in 5-day cells.

CONCLUSIONS AND CLINICAL RELEVANCE

We confirmed that T(regs) in patients with asthma are functionally impaired and that the abnormal regulatory functions of these cells can be analysed by [Ca(2+)](i) following TCR engagement. Furthermore, the impaired functioning of T(regs) evident in patients with asthma may be due to a high level of RACK1.

Regulatory T Cell Depletion Abolishes the Protective Effect of Dietary Galacto-Oligosaccharides on Eosinophilic Airway Inflammation in House Dust Mite-Induced Asthma in Mice

BACKGROUND

In a murine model for house dust mite (HDM)-induced asthma, dietary galacto-oligosaccharides have been shown to suppress allergic symptoms. Previously, CD25+ regulatory T cells (Tregs) induced by nondigestible oligosaccharides were found to protect against allergy development.

OBJECTIVE

The aim of the current study was to examine the effect of anti-CD25-induced Treg depletion in a murine HDM-induced asthma model and to study the contribution of Tregs in the protective effect of dietary intervention with galacto-oligosaccharides.

METHODS

Male BALB/c mice (aged 6-8 wk) were intranasally sensitized and challenged with phosphate-buffered saline (PBS) or HDM. Two weeks before sensitization and throughout the whole experiment, mice were fed a control or 1% w/w galacto-oligosaccharide diet. Tregs were depleted by anti-mouse CD25 antibody (intraperitoneally injected). On day 14, T helper cell subtypes in lung and spleen were analyzed and cytokines were measured. Leukocyte subtypes were analyzed in the bronchoalveolar lavage fluid, and interleukin (IL)-33 and chemokines were measured in lung homogenate supernatants.

RESULTS

Anti-CD25 treatment depleted CD25+ Forkhead box P3+ Tregs in the lung and spleen of control and HDM-allergic mice (P < 0.0001) by >70% while increasing the percentage of activated T helper cells (P < 0.05) and type 2 T helper cells (P < 0.05). This was associated with increased IL-10, IL-4, and IL-13 concentrations in supernatants of ex vivo restimulated lung cells (P < 0.01). Bronchoalveolar lavage fluid leukocyte numbers and percentages of eosinophils and lymphocytes were greater in HDM-allergic mice compared with PBS mice (P < 0.01) but remained unaffected by the anti-CD25 treatment. Galacto-oligosaccharides decreased airway eosinophilia compared with HDM-allergic mice fed the control diet (from 47.8% ± 6.7% to 26.6% ± 8.5%, P < 0.01). This protective effect was lost in anti-CD25-treated mice (P < 0.05). In lung homogenates of HDM-allergic mice, IL-33 was increased compared with PBS mice (from 2.8 ± 0.3 to 5.4 ± 0.6 ng protein/mg, P < 0.01). Galacto-oligosaccharides abrogated the increase in IL-33 compared with HDM-allergic mice fed the control diet (3.0 ± 0.6 ng protein/mg, P < 0.05), which was abolished by the anti-CD25 treatment (P < 0.01).

CONCLUSIONS

Treg depletion enhances pulmonary type 2 T helper cell frequency and cytokine release in HDM-induced asthma in mice. Galacto-oligosaccharides decreased airway eosinophilia and IL-33 concentrations in the lung, which was abrogated by Treg depletion. This indicates that galacto-oligosaccharides have a beneficial effect in the prevention of HDM-induced allergic asthma by supporting pulmonary Treg function.

The immunology of asthma

Asthma is a common disease that affects 300 million people worldwide. Given the large number of eosinophils in the airways of people with mild asthma, and verified by data from murine models, asthma was long considered the hallmark T helper type 2 (TH2) disease of the airways. It is now known that some asthmatic inflammation is neutrophilic, controlled by the TH17 subset of helper T cells, and that some eosinophilic inflammation is controlled by type 2 innate lymphoid cells (ILC2 cells) acting together with basophils. Here we discuss results from in-depth molecular studies of mouse models in light of the results from the first clinical trials targeting key cytokines in humans and describe the extraordinary heterogeneity of asthma.

Control of tissue-localized immune responses by human regulatory T cells

Treg cells control immune responses to self and nonharmful foreign antigens. Emerging data from animal models indicate that Treg cells function in both secondary lymphoid organs and tissues, and that these different microenvironments may contain specialized subsets of Treg cells with distinct mechanisms of action. The design of therapies for the restoration of tissue-localized immune homeostasis is dependent upon understanding how local immune responses are influenced by Treg cells in health versus disease. Here we review the current state of knowledge about human Treg cells in four locations: the skin, lung, intestine, and joint. Despite the distinct biology of these tissues, there are commonalities in the biology of their resident Treg cells, including phenotypic and functional differences from circulating Treg cells, and the presence of cytokine-producing (e.g. IL-17(+)) FOXP3(+) cells. We also highlight the challenges to studying tissue Treg cells in humans, and opportunities to use new technologies for the detailed analysis of Treg cells at the single-cell level. As emerging biological therapies are increasingly targeted toward tissue-specific effects, it is critical to understand their potential impact on local immune regulation.

Decreased percentage of CD4(+)Foxp3(+)TGF-β(+) and increased percentage of CD4(+)IL-17(+) cells in bronchoalveolar lavage of asthmatics

Background

Asthma is a chronic inflammatory disorder of the airways with the proven role of Th2 cells in its pathogenesis. The role and characteristic of different subsets of CD4⁺ cells is much less known.

Aim

The aim of the study was to analyze the incidence of different subsets of CD4⁺ T cells, in particular different subsets of CD4⁺ cells with the co-expression of different cytokines.

Methods

Twenty five stable asthmatic and twelve age-matched control subjects were recruited to the study. Bronchoscopy and bronchoalveolar lavage (BAL) were performed in all study subjects. CD4⁺ T cells were isolated from BAL fluid by positive magnetic selection. After stimulation simultaneous expression of TGF-β, FoxP3, CD25, IFN-γ, IL-4, TNF-α (set 1); IL-10, FoxP3, CD25, IFN-γ, IL-4, MIP-1β (set 2); IL-17A, IL-8, IFN-γ, IL-4, MIP-1β (set 3) were measured by flow cytometry.

Results

The percentage of CD4⁺ cells co-expressing Foxp3 and TGF-β (CD4⁺Foxp3⁺TGF-β⁺ cells) was significantly lower (P = 0.03), whereas the percentage of CD4⁺IL-17⁺ cells (P = 0.008), CD4⁺IL-17⁺ IFN-γ⁺ cells (P = 0.047) and CD4⁺IL-4⁺ cells (P = 0.01) were significantly increased in asthmatics compared with that seen in healthy subjects. A significantly higher percentage of CD4⁺Foxp3⁺ cells from asthma patients expressed IFN-γ (P = 0.01), IL-4 (P = 0.004) and CD25 (P = 0.04), whereas the percentage of CD4⁺IL-10⁺ cells expressing Foxp3 was significantly decreased in asthmatics (P = 0.03). FEV₁% predicted correlated negatively with the percentage of CD4⁺IL-17⁺ cells (r = -0.33; P = 0.046) and positively with CD4⁺Foxp3⁺TGF-β⁺ cells (r = 0.43; P = 0.01).

Conclusions

Our results suggest that in the airways of chronic asthma patients there is an imbalance between increased numbers of CD4⁺IL-17⁺ cells and Th2 cells and decreased number of CD4⁺Foxp3⁺TGF-β⁺.

Regulatory T cells and their roles in immune dysregulation and allergy

The main function of the immune system is to fight off potential infections, but also to maintain its activity below a level that would trigger self-reactivity. Regulatory T cells (Tregs) such as forkhead box P3(+) (FOXP3) Tregs and type 1 regulatory T cells (Tr1) play an essential role in this active process, using several distinct suppressive mechanisms. A wide range of pathologies have been associated with altered Treg cell function. This is best exemplified by the impact of mutations of genes essential for Treg function and the associated autoimmune syndromes. This review summarizes the main features of different subtypes of Tregs and focuses on the clinical implications of their altered function in human studies. More specifically, we discuss abnormalities affecting FOXP3(+) Tregs and Tr1 cells that will lead to autoimmune manifestations and/or allergic reactions, and the potential therapeutic use of Tregs.

Enhanced local Foxp3 expression in lung tissue attenuates airway inflammation in a mouse model of asthma

OBJECTIVE

Bronchial asthma is a chronic inflammatory disease of the airway mediated by a Th2 immune response. A great deal of data has demonstrated that regulatory T cells (Tregs) have the ability to suppress Th2 immune responses and the transcription factor fork-head box protein 3 (Foxp3) is indispensable for the development of CD4 + CD25 + Tregs. In this study, we hypothesized that enhanced local Foxp3 expression in lung tissue could suppress Th2-mediated allergic asthma.

METHODS

Foxp3/PMX retroviruses containing the mouse Foxp3 gene were constructed and administered into asthmatic mice through intra-tracheal instillation before ovalbumin challenging. Foxp3 expression, airway hyper-responsiveness (AHR), bronchoalveolar lavage fluid (BALF) and tissue inflammatory cell and cytokine profiles were characterized.

RESULTS

Foxp3 mRNA and protein were increased in the lung tissue of asthmatic mice. Enhanced expression of Foxp3 locally in the lung tissue reduced the airway AHR, inflammatory cell infiltration and mucus production. It also attenuated Th2 and Th17 immune responses as evidenced by reduced IL-4, IL-13 and IL-17 levels.

CONCLUSIONS

This study demonstrates that enhanced Foxp3 expression in the airway by intra-tracheally instilled Foxp3/PMX retroviruses alleviates allergic airway inflammation by reducing the Th2 immune response.

Asthma: the importance of dysregulated barrier immunity

Chronic asthma is an inflammatory disease of the airway wall that leads to bronchial smooth muscle hyperreactivity and airway obstruction, caused by inflammation, goblet cell metaplasia, and airway wall remodeling. In response to allergen presentation by airway DCs, T-helper lymphocytes of the adaptive immune system control many aspects of the disease through secretion of IL-4, IL-5, IL-13, IL-17, and IL-22, and these are counterbalanced by cytokines produced by Treg cells. Many cells of the innate immune system such as mast cells, basophils, neutrophils, eosinophils, and innate lymphoid cells also play an important role in disease pathogenesis. Barrier epithelial cells are being ever more implicated in disease pathogenesis than previously thought, as these cells have in recent years been shown to sense exposure to allergens via pattern recognition receptors and to activate conventional and inflammatory-type DCs and other innate immune cells through the secretion of thymic stromal lymphopoietin, granulocyte-macrophage colony stimulating factor, IL-1, IL-33, and IL-25. Understanding this cytokine crosstalk between barrier epithelial cells, DCs, and immune cells provides important insights into the mechanisms of allergic sensitization and asthma progression as discussed in this review.

Natural regulatory T cells in isolated early responders compared with dual responders with allergic asthma

BACKGROUND

Natural regulatory T (Treg) cells are implicated in the regulation of the inflammatory response in patients with allergic asthma.

OBJECTIVES

We sought to determine changes in Treg cell numbers in the airways and peripheral blood of isolated early responder (IER) versus dual responder (DR) subjects with mild allergic asthma before and after allergen challenge.

METHODS

Induced sputum was collected from 22 subjects with allergic asthma (10 IERs and 12 DRs) and peripheral blood collected from 8 DRs with allergic asthma at 0, 7, and 24 hours after allergen challenge. Treg cells were identified by using fluorescently labeled antibodies to CD4 and forkhead box protein 3 and enumerated by using flow cytometry.

RESULTS

There was a significant increase in the percentage of sputum CD4(+) cells 24 hours after allergen challenge in both IERs and DRs. The percentage of sputum Treg cells significantly decreased 24 hours after challenge in DRs but not IERs. This change was significantly correlated with the magnitude of the late asthmatic response. There was also a significant increase in the absolute number of sputum CD4(+) cells and Treg cells at 24 hours in DRs only. The ratio of the number of Treg cells to CD4(+) cells at 24 hours was significantly smaller in DRs compared with that in IERs. None of the above changes were observed in peripheral blood.

CONCLUSIONS

DRs exhibit a diminished percentage of airway Treg cells after allergen challenge that is not observed in IERs and a significantly lower ratio of Treg cells to CD4(+) cells, which might contribute to the development of the late asthmatic response.

Increased bronchial density of CD25+Foxp3+ regulatory T cells in occupational asthma: relationship to current smoking

To identify activated T cell subset in the asthmatic bronchia, we developed a triple-colour immunohistofluorescence labelling technique on cryo-section to discriminate activated CD4+CD25+ T cells, (effector T cells) from Foxp3+ regulatory T cells (Treg). Additional coexpression of activation and proliferation markers was also examined in situ. Bronchial biopsies were taken from 20 aluminium potroom workers (12 smokers) with asthma (>12% reversibility), 15 non-asthmatic potroom workers (7 smokers) and 10 non-smoking, non-exposed controls. Non-smoking asthmatics had significantly higher subepithelial density of both Tregs, effector T cells, activated (HLA-DR+) CD8+ and activated CD4+ T cells. Moreover, both Tregs, effector T cells and CD8+ T cells proliferated in the non-smoking asthmatics, only. Although smoking asthmatics had no asthma-associated increase in bronchial T cell, both had a significantly increase in effector T cell to Treg ratios. The significantly increased bronchial density of Tregs, effector T cells, proliferative T cells and activated CD8+ T cells in non-smoking asthmatics clearly showed that both the effector T cells and the inhibitory Treg system were activated in asthma.

Decreased CTLA4(+) and Foxp3(+) CD25(high)CD4(+) cells in induced sputum from patients with mild atopic asthma

BACKGROUND

Details of the comparisons between airway and peripheral blood regulatory T cells (Tregs) in patients with atopic asthma are still unclear. The objective of this study is to investigate the profiles of both airway and circulating Tregs in atopic asthma.

METHODS

We measured the numbers of Tregs and eosinophils in induced sputum and peripheral blood in 28 patients with mild atopic asthma and compared these with numbers in 18 healthy controls. The frequency (%) of Tregs (surface CTLA4+, intracellular Foxp3+, and CTLA4+Foxp3+ on CD25highCD4+ T cells) in sputum and blood was determined by intracellular 5-color flow cytometry. We also correlated the numbers with the level of airway hyperresponsiveness (AHR) in asthmatics.

RESULTS

The mean frequencies of cells expressing CTLA4+ (19.4 ± 2.1%, p = 0.075), Foxp3+ (16.4 ± 3.3%, p = 0.001), and CTLA4+Foxp3+ (7.0 ± 1.1%, p = 0.008) in induced sputum from asthmatics were significantly lower than controls (27.2 ± 3.7%, 37.4 ± 4.7%, and 18.2 ± 3.6%, respectively), whereas in peripheral blood, there was no inter-group difference in the frequencies of cells expressing CTLA4+ (7.1 ± 1.5% vs 5.7 ± 1.7%, p > 0.05), Foxp3+ (35.7 ± 3.2% vs 21.1 ± 3.9%, p > 0.05), and CTLA4+Foxp3+ (6.6 ± 1.5% vs 4.2 ± 1.0%, p > 0.05). Moreover, the frequency of CD25highCD4+ cells expressing CTLA4+, but not Foxp3+, in induced sputum was associated with AHR (r = 0.60, p = 0.009) and airway eosinophilic inflammation (r = -0.60, p = 0.008) in asthmatics.

CONCLUSIONS

Airway, but not circulating, Tregs are decreased in mild atopic asthmatics, and are negatively correlated to an increase of airway eosinophilic inflammation and AHR.

Gene expression signatures: a new approach to understanding the pathophysiology of chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a complex inflammatory disease with variable disease manifestation. Though external risk factors are associated with development and/or persistence of CRS, the host mucosal response is also important, as nasal epithelium acts as a physical and immune barrier. Under inflammatory stress, the nasal epithelium can undergo injury, followed by a rapid remodeling response ranging from epithelial hyperplasia, to goblet-cell metaplasia, to denudation, loss of cilia, fibrosis, and basement membrane thickening. Identification of gene expression signatures and molecular pathways in CRS pathogenesis have now begun to contribute significantly to a better understanding of the genetic and molecular alterations underlying CRS development and progression. Genetic studies are especially illuminating when multiple gene variants synergize within a permissive environmental context, and are expected to guide development of more effective therapeutic targets for CRS treatment.

Oral glucocorticoids diminish the efficacy of allergen-specific immunotherapy in experimental feline asthma

Allergen-specific rush immunotherapy (RIT) shows promise in treating asthma; however, pet cats will likely require at least initial concurrent glucocorticoids (GCs) to control serious clinical signs. How the immunosuppressive effects of GCs would impact RIT in cats is unknown. The hypothesis of this study was that oral, but not inhaled GCs will diminish the efficacy of RIT in experimental feline asthma. Cats (n=6/group) were sensitized using Bermuda grass allergen (BGA) and randomized to receive BGA-specific RIT for 9 months with an oral GC (prednisolone 10mg daily), inhaled GC (fluticasone 220 μg twice daily), or placebo administered for the first 6 months. Bronchoalveolar lavage fluid (BALF) percent eosinophils and other immunological assays were performed. Eosinophilic airway inflammation was suppressed in all groups at month 6 of RIT (group mean ± SD, 5 ± 2%, 13 ± 4%, and 7 ± 2% for oral GC, inhaled GC, and placebo, respectively; P=0.291). BALF percent eosinophils significantly increased over time only in oral GC/RIT cats between months 6 and 9 (P=0.031). Placebo/RIT cats had significant decreases over time in BGA-specific serum IgE (P=0.031). Concentration of interleukin (IL)-5 in BALF significantly increased over time in inhaled GC/RIT cats (P=0.031). No significant differences were found between groups at month 6 or over time in each group for BGA-specific lymphocyte blastogenesis, percent blood T regulatory cells, or number of IL-10-producing cells. Given the significant increase of airway eosinophilia over time in RIT cats initially treated with an oral GC, inhaled GCs might be better for dampening eosinophilic inflammation until RIT normalizes the dysregulated immune system.

Enhanced generation of suppressor T cells in patients with asthma taking oral contraceptives

Introduction. A dysregulation of regulatory T cells (Tregs) could play a major role in the pathogenesis of bronchial asthma. Sex-dependent differences as well as the impact of hormonal changes in the incidence and severity of asthma are widely recognized. Emerging evidence suggests that asthma symptoms are alleviated in female patients taking hormone oral contraceptives (OCs). The impact of OCs on the generation of induced Tregs (iTregs) was assessed in a cohort of female patients with asthma. Methods. Thirteen patients were included in this pilot study. During three distinct phases of their menstrual cycles, we measured exhaled nitric oxide (eNO) levels, forced expiratory volume at 1 second (FEV1s), asthma control test (ACT) score, sex steroid hormone levels in serum, natural Tregs in peripheral blood, and the ability of CD4(+) T cells to generate iTregs ex vivo. Results. The luteal serum levels of estradiol and progesterone negatively correlated with the proportion of iTregs generated ex vivo in patients not taking OCs. In addition, physiological doses of estradiol and progesterone prevented the acquisition of a suppressor T cell phenotype in vitro. Interestingly, patients taking OCs had reduced serum sex hormone levels associated with higher iTreg induction, a better ACT score, and a tendency toward lower eNO levels. Conclusions. Our results identify an impact of sex hormones on the capacity of T cells to polarize towards a regulatory phenotype and suggest the regulation of peripheral T cell lineage plasticity as a potential mechanism underlying the beneficial effects of OCs in women with asthma.

Mechanisms of peripheral tolerance to allergens

The immune system is regulated to protect the host from exaggerated stimulatory signals establishing a state of tolerance in healthy individuals. The disequilibrium in immune regulatory vs effector mechanisms results in allergic or autoimmune disorders in genetically predisposed subjects under certain environmental conditions. As demonstrated in allergen-specific immunotherapy and in the healthy immune response to high-dose allergen exposure models in humans, T regulatory cells are essential in the suppression of Th2-mediated inflammation, maintenance of immune tolerance, induction of the two suppressive cytokines interleukin-10 and transforming growth factor-β, inhibition of allergen-specific IgE, and enhancement of IgG4 and IgA. Also, suppression of dendritic cells, mast cells, and eosinophils contributes to the construction of peripheral tolerance to allergens. This review focuses on mechanisms of peripheral tolerance to allergens with special emphasis on recent developments in the area of immune regulation.

Inhaled corticosteroid use is associated with increased circulating T regulatory cells in children with asthma

BACKGROUND

T regulatory (Treg) cells are important in balancing immune responses and dysregulation of Treg cells has been implicated in the pathogenesis of multiple disease states including asthma. In this study, our primary aim was to determine Treg cell frequency in the peripheral blood of children with and without asthma. The secondary aim was to explore the association between Treg cell frequency with allergen sensitization, disease severity and medication use.

METHODS

Peripheral blood mononuclear cells from healthy control subjects (N = 93) and asthmatic children of varying disease severity (N = 66) were characterized by multi-parameter flow cytometry.

RESULTS

Our findings demonstrate that children with asthma had a significantly increased frequency of Treg cells compared to children without asthma. Using a multivariate model, increased Treg cell frequency in children with asthma was most directly associated with inhaled corticosteroid use, and not asthma severity, allergic sensitization, or atopic status of the asthma.

CONCLUSION

We conclude that low dose, local airway administration of corticosteroids is sufficient to impact the frequency of Treg cells in the peripheral blood. These data highlight the importance of considering medication exposure when studying Treg cells and suggest inhaled corticosteroid use in asthmatics may improve disease control through increased Treg cell frequency.

Experimental advances in understanding allergic airway inflammation

Asthma is largely an inflammatory disease, with the development of T cell mediated inflammation in the lung following exposure to allergen or other precipitating factors. Currently, the major therapies for this disease are directed either at relief of bronchoconstriction (ie beta-agonists) or are non-specific immunomodulators (ie, corticosteroids). While much attention has been paid to factors that regulate the initiation of an inflammatory response, chronic inflammation may also be due to defects in regulatory mechanisms that limit or terminate immune responses. In this review, we explore the elements controlling both the recruitment of T cells to the lung and their function. Possibilities for future therapeutic intervention are highlighted.

Immunophenotyping of circulating T helper cells argues for multiple functions and plasticity of T cells in vivo in humans--possible role in asthma

Background

The immune process driving eosinophilic and non-eosinophilic asthma is likely driven by different subsets of T helper (Th) cells. Recently, in vitro studies and animal studies suggest that Th cell subsets displays plasticity by changing their transcription factor or by expressing multiple transcription factors. Our aim was to determine whether individuals with asthma and elevated circulating eosinophils express signs of different regulatory immune mechanisms compared with asthmatics with low blood eosinophils and non-asthmatic control subjects. In addition, determine the relationship between eosinophilia and circulating Th cell subsets.

Methodology/Principal findings

Participants were selected from a random epidemiological cohort, the West Sweden Asthma Study. Immunophenotypes of fresh peripheral blood cells obtained from stable asthmatics, with and without elevated eosinophilic inflammation (EOS high and EOS low respectively) and control subjects, were determined by flow cytometry. No differences in the number of Th1 (T-bet), Th2 (GATA-3), Th17 (RORγt) or Treg (FOXP3) cells were observed between the groups when analysing each subset separately. However, in all groups, each of the Th subsets showed expression of additional canonical transcription factors T-bet, GATA-3, RORγt and FOXP3. Furthermore, by in vitro stimulation with anti-CD3/anti-CD28 there was a significant increase of single expressing GATA-3⁺ and co-expressing T-bet⁺GATA-3⁺ cells in the EOS high asthmatics in comparison with control subjects. In addition, T-bet⁻GATA-3⁺RORγt⁺FOXP3⁺ were decreased in comparison to the EOS low asthmatics. Finally, in a group of control subjects we found that the majority of proliferating Th cells (CD4⁺CD25⁺Ki67⁺) expressed three or four transcription factors.

Conclusions

The ability of human Th cells to express several regulatory transcription factors suggests that these cells may display plasticity in vivo.