Neuromedin-U Mediates Rapid Activation of Airway Group 2 Innate Lymphoid Cells in Mild Asthma.

RATIONALE: In asthma, sputum group 2 innate lymphoid cells (ILC2) are activated within 7h after allergen challenge. Neuroimmune interactions mediate rapid host responses at mucosal interfaces. In murine models of asthma, lung ILC2 co-localize to sensory neuronal termini expressing the neuropeptide, neuromedin U (NMU) and NMU stimulates type 2 cytokines secretion by ILC2 with additive effects to alarmins, in vitro. OBJECTIVES: Investigate effect of NMU/NMUR1 axis on early activation of ILC2 in asthma. METHODS: M ild asthmatics (n=8) were enrolled in a diluent-controlled, allergen-inhalation challenge study. Sputum ILC2 expression of NMU receptor 1 (NMUR1) and T2 cytokines were enumerated by flow cytometry and airway NMU levels were assessed by ELISA. This was compared to samples from moderate-severe asthmatics (n=9). Flow sort-purified and ex-vivo expanded ILC2 were used for functional assays and transcriptomic analyses. RESULTS: Significant increases in sputum ILC2 expressing NMUR1 were detected 7h post- allergen versus diluent challenge where the majority of NMUR1+ILC2 expressed IL-5/IL-13. Sputum NMUR1+ILC2 were significantly greater in mild versus moderate-severe asthmatics and NMUR1+ILC2 correlated inversely with the dose of inhaled corticosteroid in the latter group. Co-culturing with alarmins upregulated NMUR1 in ILC2, which was attenuated by dexamethasone. NMU stimulated T2 cytokine expression by ILC2, maximal at 6h was abrogated by dexamethasone or specific signaling inhibitors for mitogen-activated protein kinase ½, phospho-inositol 3 kinase but not IL-33 signaling moiety MyD88, in vitro. CONCLUSIONS: The NMU/NMUR1 axis stimulates rapid effects on ILC2, and maybe an important early activator of these cells in eosinophilic inflammatory responses in asthma.

Benralizumab for allergic asthma: a randomised, double-blind, placebo-controlled, trial.

RATIONALE AND OBJECTIVE: Benralizumab induces rapid and near-complete depletion of eosinophils from blood and lung tissue. We investigated whether benralizumab could attenuate allergen-induced late asthmatic responses (LAR) in participants with allergic asthma. METHODS AND MEASUREMENTS: Participants with allergic asthma who demonstrated increased sputum eosinophils and LAR at screening were randomised to benralizumab 30 mg or matched placebo given every 4 weeks for 8 weeks (3 doses). Allergen challenges were performed at weeks 9 and 12 when blood, sputum, bone marrow and bronchial tissue eosinophils and LAR were assessed. MAIN RESULTS: Forty-six participants (mean age, 30.9 years) were randomised to benralizumab (n = 23) or placebo (n = 23). Eosinophils were significantly reduced in the benralizumab group compared with placebo in blood at 4 weeks and sputum and bone marrow at 9 weeks after treatment initiation. At 7 h after an allergen challenge at week 9, sputum eosinophilia was significantly attenuated in the benralizumab group compared to placebo (least squares mean difference -5.81% [95% CI, -10.69, -0.94]; P = 0.021); however, the LAR was not significantly different (least squares mean difference 2.54% [95% CI, 3.05, 8.12]; P = 0.363). Adverse events were reported for 7 (30.4%) and 14 (60.9%) participants in the benralizumab and placebo groups, respectively. CONCLUSION: Benralizumab administration over 8 weeks resulted in a significant attenuation of blood, bone marrow and sputum eosinophilia in participants with mild allergic asthma; however, there was no change in the LAR, suggesting that eosinophils alone are not a key component of allergen-induced bronchoconstriction.

Efficacy of Biologics in Patients with Allergic Bronchopulmonary Aspergillosis: A Systematic Review and Meta-Analysis.

BACKGROUND: Treatment of allergic bronchopulmonary aspergillosis (ABPA) is challenging. Biological therapies have been reported as adjunctive treatments for ABPA, primarily in case series or case reports. This study aimed to analyze the efficacy of biologics for managing ABPA both qualitatively and quantitatively. METHODS: All articles on APBA published in October 2023 were searched in PubMed, Web of Science, ClinicalTrials.gov, and Embase databases. The effects of interest were the mean changes from baseline for outcomes, including exacerbation rates, oral corticosteroids usage (OCS), and total immunoglobulin E (IgE) levels. Reported outcomes were quantitatively synthesized by usual or individual patient data (IPD) meta-analyses. PROSPERO registration number: CRD42022373396. RESULTS: A total of 86 studies were included in the systematic review including 346 patients. Sixteen studies on omalizumab were pooled for the usual meta-analysis. Omalizumab therapy significantly reduced exacerbation rates (- 2.29 [95%CI - 3.32, - 1.26]), OCS dosage (- 10.91 mg [95%CI - 18.98, - 2.85]), and total IgE levels (- 273.07 IU/mL [95%CI - 379.30, - 166.84]), meanwhile improving FEV1% predicted (10.09% [95%CI 6.62, 13.55]). Thirty-one studies on dupilumab, mepolizumab, or benralizumab were pooled to perform an IPD meta-analysis, retrospectively. Both dupilumab and mepolizumab significantly reduced exacerbation rates, OCS, and total IgE levels. Benralizumab showed a similar trend, but it was not statistically significant. Tezepelumab showed weak evidence of its effects on ABPA. All five biologics led to milder clinical symptoms (e.g., cough, wheezing) with serious adverse effects that happened once in omalizumab treatment. CONCLUSION: These results indicate the clinical benefit of omalizumab, dupilumab, and mepolizumab in patients with ABPA. Further randomized, controlled studies with a larger sample size and longer follow-up are needed to confirm these findings.

Immune Response Dynamics and Biomarkers in COVID-19 Patients.

BACKGROUND: The immune response dynamics in COVID-19 patients remain a subject of intense investigation due to their implications for disease severity and treatment outcomes. We examined changes in leukocyte levels, eosinophil activity, and cytokine profiles in patients hospitalized with COVID-19. METHODS: Serum samples were collected within the first 10 days of hospitalization/confirmed infection and analyzed for eosinophil granule proteins (EGP) and cytokines. Information from medical records including comorbidities, clinical symptoms, medications, and complete blood counts were collected at the time of admission, during hospitalization and at follow up approximately 3 months later. RESULTS: Serum levels of eotaxin, type 1 and type 2 cytokines, and alarmin cytokines were elevated in COVID-19 patients, highlighting the heightened immune response (p < 0.05). However, COVID-19 patients exhibited lower levels of eosinophils and eosinophil degranulation products compared to hospitalized controls (p < 0.05). Leukocyte counts increased consistently from admission to follow-up, indicative of recovery. CONCLUSION: Attenuated eosinophil activity alongside elevated chemokine and cytokine levels during active infection, highlights the complex interplay of immune mediators in the pathogenesis COVID-19 and underscores the need for further investigation into immune biomarkers and treatment strategies.

Evaluation of the reproducibility of responses to nasal allergen challenge and effects of inhaled nasal corticosteroids.

BACKGROUND: Similar immune responses in the nasal and bronchial mucosa implies that nasal allergen challenge (NAC) is a suitable early phase experimental model for drug development targeting allergic rhinitis (AR) and asthma. We assessed NAC reproducibility and the effects of intranasal corticosteroids (INCS) on symptoms, physiology, and inflammatory mediators. METHODS: 20 participants with mild atopic asthma and AR underwent three single blinded nasal challenges each separated by three weeks (NCT03431961). Cohort A (n = 10) underwent a control saline challenge, followed by two allergen challenges. Cohort B (n = 10) underwent a NAC with no treatment intervention, followed by NAC with 14 days pre-treatment with saline nasal spray (placebo), then NAC with 14 days pre-treatment with INCS (220 µg triamcinolone acetonide twice daily). Nasosorption, nasal lavage, blood samples, forced expiratory volume 1 (FEV1), total nasal symptom score (TNSS), peak nasal inspiratory flow (PNIF) were collected up to 24 h after NAC. Total and active tryptase were measured as early-phase allergy biomarkers (≤30 min) and IL-13 and eosinophil cell counts as late-phase allergy biomarkers (3-7 h) in serum and nasal samples. Period-period reproducibility was assessed by intraclass correlation coefficients (ICC), and sample size estimates were performed using effect sizes measured after INCS. RESULTS: NAC significantly induced acute increases in nasosorption tryptase and TNSS and reduced PNIF, and induced late increases in nasosorption IL-13 with sustained reductions in PNIF. Reproducibility across NACs varied for symptoms and biomarkers, with total tryptase 5 min post NAC having the highest reproducibility (ICC = 0.91). Treatment with INCS inhibited NAC-induced IL-13 while blunting changes in TNSS and PNIF. For a similar crossover study, 7 participants per treatment arm are needed to detect treatment effects comparable to INCS for TNSS. CONCLUSION: NAC-induced biomarkers and symptoms are reproducible and responsive to INCS. NAC is suitable for assessing pharmacodynamic activity and proof of mechanism for drugs targeting allergic inflammation.

Sounding the alarmins-The role of alarmin cytokines in asthma.

The alarmin cytokines thymic stromal lymphopoietin (TSLP), interleukin (IL)-33, and IL-25 are epithelial cell-derived mediators that contribute to the pathobiology and pathophysiology of asthma. Released from airway epithelial cells exposed to environmental triggers, the alarmins drive airway inflammation through the release of predominantly T2 cytokines from multiple effector cells. The upstream positioning of the alarmins is an attractive pharmacological target to block multiple T2 pathways important in asthma. Blocking the function of TSLP inhibits allergen-induced responses including bronchoconstriction, airway hyperresponsiveness, and inflammation, and subsequent clinical trials of an anti-TSLP monoclonal antibody, tezepelumab, in asthma patients demonstrated improvements in lung function, airway responsiveness, inflammation, and importantly, a reduction in the rate of exacerbations. Notably, these improvements were observed in patients with T2-high and with T2-low asthma. Clinical trials blocking IL-33 and its receptor ST2 have also shown improvements in lung function and exacerbation rates; however, the impact of blocking the IL-33/ST2 axis in T2-high versus T2-low asthma is unclear. To date, there is no evidence that IL-25 blockade is beneficial in asthma. Despite the considerable overlap in the cellular functions of IL-25, IL-33, and TSLP, they appear to have distinct roles in the immunopathology of asthma.

Granzyme K contributes to endothelial microvascular damage and leakage during skin inflammation.

BACKGROUND: Granzyme K (GzmK) is a serine protease with minimal presence in healthy tissues while abundant in inflamed tissues. Initially thought to play an exclusive role in immune-mediated cell death, extracellular GzmK can also promote inflammation. OBJECTIVES: To evaluate the role of GzmK in the pathogenesis of atopic dermatitis (AD), the most common inflammatory skin disease. METHODS: A panel of human AD and control samples was analysed to determine if GzmK is elevated. Next, to determine a pathological role for GzmK in AD-like skin inflammation, oxazolone-induced dermatitis was induced in GzmK-/- and wild-type (WT) mice. RESULTS: In human lesional AD samples, there was an increase in the number of GzmK+ cells compared with healthy controls. GzmK-/- mice exhibited reduced overall disease severity characterized by reductions in scaling, erosions and erythema. Surprisingly, the presence of GzmK did not notably increase the overall pro-inflammatory response or epidermal barrier permeability in WT mice; rather, GzmK impaired angiogenesis, increased microvascular damage and microhaemorrhage. Mechanistically, GzmK contributed to vessel damage through cleavage of syndecan-1, a key structural component of the glycocalyx, which coats the luminal surface of vascular endothelia. CONCLUSIONS: GzmK may provide a potential therapeutic target for skin conditions associated with persistent inflammation, vasculitis and pathological angiogenesis.

Effect of intranasal corticosteroid treatment on allergen-induced changes in group 2 innate lymphoid cells in allergic rhinitis with mild asthma.

BACKGROUND: Allergic rhinitis is characterized by rhinorrhea, nasal congestion, sneezing and nasal pruritus. Group 2 innate lymphoid cells (ILC2s), CD4+ T cells and eosinophils in nasal mucosa are increased significantly after nasal allergen challenge (NAC). Effects of intranasal corticosteroids (INCS) on ILC2s remain to be investigated. METHODS: Subjects (n = 10) with allergic rhinitis and mild asthma were enrolled in a single-blind, placebo-controlled, sequential treatment study and treated twice daily with intranasal triamcinolone acetonide (220 µg) or placebo for 14 days, separated by a 7-day washout period. Following treatment, subjects underwent NAC and upper airway function was assessed. Cells from the nasal mucosa and blood, sampled 24 h post-NAC, underwent flow cytometric enumeration for ILC2s, CD4+ T and eosinophil progenitor (EoPs) levels. Cell differentials and cytokine levels were assessed in nasal lavage. RESULTS: Treatment with INCS significantly attenuated ILC2s, IL-5+ /IL-13+ ILC2s, HLA-DR+ ILC2s and CD4+ T cells in the nasal mucosa, 24 h post-NAC. EoP in nasal mucosa was significantly increased, while mature eosinophils were significantly decreased, 24 h post-NAC in INCS versus placebo treatment arm. Following INCS treatment, IL-2, IL-4, IL-5 and IL-13 were significantly attenuated 24 h post-NAC accompanied by significant improvement in upper airway function. CONCLUSION: Pre-treatment with INCS attenuates allergen-induced increases in ILC2s, CD4+ T cells and terminal differentiation of EoPs in the nasal mucosa of allergic rhinitis patients with mild asthma, with little systemic effect. Attenuation of HLA-DR expression by ILC2s may be an additional mechanism by which steroids modulate adaptive immune responses in the upper airways.

The Role of the TL1A/DR3 Axis in the Activation of Group 2 Innate Lymphoid Cells in Subjects with Eosinophilic Asthma.

Rationale: Group 2 innate lymphoid cells (ILC2s) are critical for type 2 inflammation. In murine models of asthma, some ILC2s remain activated in the absence of epithelial cell-derived cytokine signaling, implicating alternate stimulatory pathways. DR3 (death receptor 3), a member of the tumor necrosis factor receptor superfamily, is expressed on ILC2s. Genome-wide association studies report an association between DR3 ligand, TL1A (tumor necrosis factor-like protein 1A), and chronic inflammatory conditions.Objectives: We investigated the TL1A/DR3 axis in airway ILC2 biology in eosinophilic asthma.Methods: Stable subjects with mild asthma were subject to allergen inhalation challenge, and DR3 expression on sputum cells was assessed. We investigated cytokine regulation of DR3 expression on ILC2s and steroid sensitivity. Airway TL1A was assessed in sputum from subjects with mild asthma and subjects with prednisone-dependent severe eosinophilic asthma.Measurements and Main Results: There was a significant increase in sputum DR3+ ILC2s 24 hours after allergen challenge, and DR3 expression on ILC2s was upregulated by IL-2, IL-33, or TSLP in vitro. Stimulation with TL1A significantly increased IL-5 expression by ILC2s and was attenuated by dexamethasone, an effect that was negated in the presence of TSLP. Airway TL1A levels were increased 24 hours after allergen challenge in subjects with mild asthma but were significantly greater in those with severe eosinophilic asthma. The highest levels were detected in subjects with severe asthma with airway autoimmune responses. C1q+ immune complexes from the sputa of subjects with severe asthma with high autoantibody levels stimulated TL1A production by monocytes.Conclusions: The TL1A/DR3 axis is a costimulator of ILC2s in asthma, particularly in the airways of patients with a predisposition to autoimmune responses.

Atopic March: Collegium Internationale Allergologicum Update 2020.

In recent decades, the worldwide prevalence of allergic disease has increased considerably. The atopic march is a model aimed at explaining the apparent progression of allergic diseases from atopic dermatitis (AD) to allergic asthma (AA) and to allergic rhinitis (AR). It hypothesizes that allergic disease begins, typically in children, with the development of AD, then AA, and finally progresses to AR. This theory has been widely studied in cross-sectional and long-term longitudinal studies and it has been found that as prevalence of AD declines, prevalence of AA increases. A similar relationship is reported between AA and AR. The legitimacy of the atopic march model is, however, currently debated. Epidemiological evidence and criticism of longitudinal studies point to an overstatement of the atopic march's prevalence and incorrect mechanisms, opening a discussion for alternative models to better explain the pathophysiological and epidemiological processes that promote this progression of allergic diseases. Albeit, risk factors for the development and progression of allergic disease, particularly AD, are critical in identifying disease progression. Investigating the role of age, severity, family history, phenotype, and genetic traits may give a better indication into the progression of allergic diseases. In addition, studies following patients from infancy into adulthood and a general increase in longitudinal studies would help broaden the knowledge of allergic disease progression and the atopic march.

Weight-adjusted Intravenous Reslizumab in Severe Asthma with Inadequate Response to Fixed-Dose Subcutaneous Mepolizumab.

RATIONALE: Clinical benefits of fixed-dose 100-mg subcutaneous (SC) mepolizumab in prednisone-dependent patients are modest when sputum eosinophilia is not adequately controlled. OBJECTIVES: This study compared treatment response of weight-adjusted intravenous (IV) reslizumab in patients previously treated with 100-mg SC mepolizumab. METHODS: Ten prednisone-dependent patients with asthma (sputum eosinophils >3% and blood eosinophils >300 cells/µl), who had previously received mepolizumab (100 mg SC dosed every 4 wk [Q4W]) for at least 1 year, received two infusions of placebo (Q4W) followed by four infusions of 3.0 mg/kg reslizumab Q4W in a single-blind, placebo-controlled sequential trial. Primary outcomes were reduction of eosinophils in sputum and blood. Additional outcomes included FEV1, asthma control questionnaire, eosinophil peroxidase, IL-5, sputum and blood innate lymphoid cells group 2, eosinophil progenitor cells, and autoimmune responses. MEASUREMENTS AND MAIN RESULTS: IV reslizumab attenuated sputum eosinophils by 91.2% (P = 0.002), blood eosinophil counts by 87.4% (P = 0.004), and sputum eosinophil peroxidase levels by 65.5% (P = 0.03) compared with placebo. Attenuation of both local and systemic eosinophilia was associated with statistically significant improvements in FEV1 (P = 0.004) and asthma control questionnaire five-question instrument scores (P = 0.006). Decrease in percent sputum eosinophil was greater with reslizumab (by 42.7%) compared with mepolizumab (by 5.0%) and this was associated with greater improvement in asthma control questionnaire (P = 0.01; analysis of covariance of Δ between before and after treatment, mepolizumab vs. reslizumab, adjusted for baseline prednisone). Changes in sputum IL-5 and anti-eosinophil peroxidase IgG after anti-IL-5 therapy were predictors of response. CONCLUSIONS: Weight-adjusted IV reslizumab was superior to fixed-dose SC mepolizumab in attenuating airway eosinophilia in prednisone-dependent patients with asthma, with associated improvement in asthma control. Clinical trial registered with www.clinicaltrials.gov (NCT 02559791).

Human Bronchial Epithelial Cell-derived Factors from Severe Asthmatic Subjects Stimulate Eosinophil Differentiation.

Activated bronchial epithelial cells (BEC) release various alarmins, including thymic stromal lymphopoietin (TSLP), that drive type 2 inflammation. We hypothesize that BEC-derived factors promote in situ eosinophil differentiation and maturation, a process that is driven by an IL-5-rich microenvironment in asthmatic airways. To assess the eosinophilopoietic potential of epithelial-derived factors, eosinophil/basophil colony forming units (Eo/B-CFU) were enumerated in 14-day methylcellulose cultures of blood-derived nonadherent mononuclear cells incubated with BEC supernatants (BECSN) from healthy nonatopic controls (n = 8), mild atopic asthmatics (n = 9), and severe asthmatics (n = 5). Receptor-blocking antibodies were used to evaluate the contribution of alarmins. Modulation of the mRNA expression of transcription factors that are crucial for eosinophil differentiation was evaluated. BECSN stimulated the clonogenic expansion of eosinophil progenitors in vitro. In the presence of IL-5, Eo/B-CFU numbers were significantly greater in cocultures of BESCN from severe asthmatics compared with other groups. This was attenuated in the presence of a TSLP (but not an IL-33) receptor-blocking antibody. Recombinant human TSLP (optimal at 100 pg/ml) stimulated Eo/B-CFU growth, which was significantly enhanced in the presence of IL-5 (1 ng/ml). Overnight culture of CD34+ cells with IL-5 and TSLP synergistically increased GATA-binding factor 2 and CCAAT/enhancer-binding protein α mRNA expression. The eosinophilopoietic potential of factors derived from BEC is increased in severe asthma. Our data suggest that TSLP is a key alarmin that is produced by BECs and promotes in situ eosinophilopoiesis in a type 2-rich microenvironment.

IL-33 and Its Receptor ST2 after Inhaled Allergen Challenge in Allergic Asthmatics.

BACKGROUND: Previous murine models have demonstrated interleukin (IL)-33 to be an important mediator of type-2 inflammation and to promote airway hyperresponsiveness in allergic asthma. A number of inflammatory cells produce IL-33 and eosinophils express ST2 mRNA. The relationship between IL-33 and eosinophils in allergic asthma, however, remains unclear. OBJECTIVE: The aim of this work was to evaluate in vitro the effect of allergen inhalation on IL-33 levels and expression of its receptor (ST2L) on eosinophils in allergic asthmatics, and the effect of IL-33 stimulation on eosinophil activity. METHODS: Plasma and sputum IL-33, soluble ST2 (sST2) levels, and ST2L expression on eosinophils were measured in 10 healthy controls and 10 allergic asthmatics. Asthmatics underwent allergen and diluent inhalation challenges. Blood and sputum samples were collected to measure IL-33, sST2, and ST2L eosinophil expression before and 24 h after allergen inhalation. Purified blood eosinophils from allergic asthmatics were incubated overnight with IL-33 to assess ST2 and intracellular IL-5 expression. RESULTS: Baseline levels of IL-33 in sputum and sST2 in plasma and sputum were similar in allergic asthmatics compared to healthy controls. In addition, there was no difference in blood or sputum eosinophil ST2L expression in healthy controls versus allergic asthmatics. Eosinophil ST2L expression was significantly increased 24 h postallergen inhalation in allergic asthmatics. In vitro stimulation of human eosinophils with IL-33 and LPS significantly increased eosinophil ST2L expression and IL-33 stimulation increased intracellular IL-5 expression, which was attenuated by treatment with sST2 and ST2 blockade. CONCLUSION AND CLINICAL RELEVANCE: In mild asthmatics, there was a significant upregulation of ST2 surface expression on eosinophils from blood and sputum following allergen inhalation challenge. In vitro, IL-33 stimulation of eosinophils increases both ST2 membrane expression and IL-5 production. These results support a role for IL-33 in causing allergen-induced eosinophilia. Blockade of IL-33 and ST2 signaling may present a novel therapeutic avenue for asthma treatment.

Antialarmins for treatment of asthma: future perspectives.

PURPOSE OF REVIEW: Recent studies have highlighted the role of alarmins in asthma pathophysiology and tested the roles of these cytokines in asthmatic patients. This review will discuss the recent advances in the role of alarmins in asthma and the potential of future targeted therapies in asthma. RECENT FINDINGS: Epithelial-derived cytokines can be released upon exposure to external stimuli, causing damage to the epithelial barrier and resulting in tissue inflammation. Of these cytokines, IL-25, IL-33 and thymic stromal lymphopoeitin (TSLP), have been associated with asthma. These alarmins are all not only overexpressed in asthmatic airways, particularly in airway epithelial cells, but also in other structural and immune cells. Furthermore, all three alarmins drive type-2 pro-inflammatory responses in several immune cells that have been identified as key players in the pathogenesis of asthma, including innate lymphoid type-2 cells. Clinical trials testing therapeutics that block pathways of the alarmins are in progress. SUMMARY: To-date, only TSLP blockade has been reported in human clinical trials, and this approach has shown efficacy in asthmatic patients. Current body of evidence suggests that alarmins are useful upstream targets for treatment of asthma.

Allergen-induced Increases in Sputum Levels of Group 2 Innate Lymphoid Cells in Subjects with Asthma.

RATIONALE: Group 2 innate lymphoid cells (ILC2), a major source of type 2 cytokines, initiate eosinophilic inflammatory responses in murine models of asthma. OBJECTIVES: To investigate the role of ILC2 in allergen-induced airway eosinophilic responses in subjects with atopy and asthma. METHODS: Using a diluent-controlled allergen challenge crossover study, where all subjects (n = 10) developed allergen-induced early and late responses, airway eosinophilia, and increased methacholine airway responsiveness, bone marrow, blood, and sputum samples were collected before and after inhalation challenge. MEASUREMENTS AND MAIN RESULTS: ILC2 (lin-FcεRI-CD45+CD127+ST2+) and CD4+T lymphocytes were enumerated by flow cytometry, as well as intracellular IL-5 and IL-13 expression. Steroid sensitivity of ILC2 and CD4+ T cells was investigated in vitro. A significant increase in total, IL-5+, IL-13+, and CRTH2+ ILC2 was found in sputum, 24 hours after allergen, coincident with a significant decrease in blood ILC2. Total, IL-5+, and IL-13+, but not CRTH2+, CD4+ T cells significantly increased at 24 and 48 hours after allergen in sputum. In blood and bone marrow, only CD4+ cells demonstrated increased activation after allergen. Airway eosinophilia correlated with IL-5+ ILC2 at all time points and allergen-induced changes in IL-5+ CD4+ cells at 48 hours after allergen. Dexamethasone significantly attenuated IL-2- and IL-33-stimulated IL-5 and IL-13 production by both cell types. CONCLUSIONS: Innate and adaptive immune cells are increased in the airways associated with allergic asthmatic responses. Total and type 2 cytokine-positive ILC2 are increased only within the airways, whereas CD4+ T lymphocytes demonstrated local and systemic increases. Steroid sensitivity of both cells may explain effectiveness of this therapy in those with mild asthma.