Glucocorticoids decrease Treg cell numbers in lungs of allergic mice

Gentisic acid attenuates ovalbumin-induced airway inflammation, oxidative stress, and ferroptosis through the modulation of Nrf2/HO-1 and NF-κB signaling pathways

Asthma, a lung disorder that causes impaired respiratory function, is characterized by an apparent infiltration of inflammatory cells. Gentisic acid (GA), a phenolic acid common in food ingredients, has antioxidant, antibacterial, and anti-inflammatory properties. Its potential application in mitigating asthma, however, remains unexplored. The current investigation studies GA's therapeutic potential for allergic asthma. BALB/c mice were challenged and sensitized to ovalbumin (OVA) to establish the animal model. We investigated how GA affected asthmatic behavior, leukocyte infiltration, histopathological alterations, oxidative stress, immunoglobulin E (IgE) production, and airway inflammation. ELISA and immunohistochemistry (IHC) techniques were employed to measure Nrf2, HO-1, and NF-κB's expression. To investigate the protein-ligand interaction between GA and Keap1, molecular docking analysis was utilized. The GA treatment significantly reduced nasal scratching, oxidative stress in the lungs, the infiltration of inflammatory cells, IgE content, iron accumulation, and NF-κB activation. It also upregulated Nrf2 and HO-1. Additionally, in silico studies revealed GA and Keap1 binding to activate Nrf2 by disrupting the Keap1-Nrf2 interaction. The study at hand is the first to investigate and report on the immunomodulatory impacts of GA on induced asthma in BALB/c mice. Our findings reveal that GA can be utilized as an anti-asthmatic agent via Nrf2/HO-1 and NF-κB pathway regulation.

Journey through discovery of 75 years glucocorticoids: evolution of our knowledge of glucocorticoid receptor mechanisms in rheumatic diseases

For three-quarters of a century, glucocorticoids (GCs) have been used to treat rheumatic and autoimmune diseases. Over these 75 years, our understanding of GCs binding to nuclear receptors, mainly the glucocorticoid receptor (GR) and their molecular mechanisms has changed dramatically. Initially, in the late 1950s, GCs were considered important regulators of energy metabolism. By the 1970s/1980s, they were characterised as ligands for hormone-inducible transcription factors that regulate many aspects of cell biology and physiology. More recently, their impact on cellular metabolism has been rediscovered. Our understanding of cell-type-specific GC actions and the crosstalk between various immune and stromal cells in arthritis models has evolved by investigating conditional GR mutant mice using the Cre/LoxP system. A major achievement in studying the complex, cell-type-specific interplay is the recent advent of omics technologies at single-cell resolution, which will provide further unprecedented insights into the cell types and factors mediating GC responses. Alongside gene-encoded factors, anti-inflammatory metabolites that participate in resolving inflammation by GCs during arthritis are just being uncovered. The translation of this knowledge into therapeutic concepts will help tackle inflammatory diseases and reduce side effects. In this review, we describe major milestones in preclinical research that led to our current understanding of GC and GR action 75 years after the first use of GCs in arthritis.

Impact of inflammation and Treg cell regulation on neuropathic pain in spinal cord injury: mechanisms and therapeutic prospects

Spinal cord injury is a severe neurological trauma that can frequently lead to neuropathic pain. During the initial stages following spinal cord injury, inflammation plays a critical role; however, excessive inflammation can exacerbate pain. Regulatory T cells (Treg cells) have a crucial function in regulating inflammation and alleviating neuropathic pain. Treg cells release suppressor cytokines and modulate the function of other immune cells to suppress the inflammatory response. Simultaneously, inflammation impedes Treg cell activity, further intensifying neuropathic pain. Therefore, suppressing the inflammatory response while enhancing Treg cell regulatory function may provide novel therapeutic avenues for treating neuropathic pain resulting from spinal cord injury. This review comprehensively describes the mechanisms underlying the inflammatory response and Treg cell regulation subsequent to spinal cord injury, with a specific focus on exploring the potential mechanisms through which Treg cells regulate neuropathic pain following spinal cord injury. The insights gained from this review aim to provide new concepts and a rationale for the therapeutic prospects and direction of cell therapy in spinal cord injury-related conditions.

ICS/LABA Combined With Subcutaneous Immunotherapy Modulates the Th17/Treg Imbalance in Asthmatic Children

Rationale

The imbalance of T helper (Th17) cell and regulatory T (Treg) cell are involved in allergic asthma pathogenesis. We hypothesized that ICS/LABA could modulate the Th17/Treg imbalance and that subcutaneous immunotherapy (SCIT) could coordinate with ICS/LABA to rebalance the dysfunction of Th17/Treg.

Methods

Thirty house dust mites (HDM) allergic asthmatic children and fifteen healthy control subjects were enrolled in this study. Fifteen asthmatic children were treated by ICS/LABA powder inhalation, while the other fifteen asthmatic children were treated by ICS/LABA powder inhalation combined with HDM-SCIT. Asthmatic subjects were followed up for 6 months, but 2 asthmatics treated with ICS/LABA were lost to follow-up. Flow cytometry was used to determine the proportions of Th17 and Treg in CD4⁺ T cells from peripheral blood mononuclear cells (PBMCs). Serum levels of IL-17A and IL-10 were assessed by ELISA.

Result

ICS/LABA treatment significantly reduced the percentage of Th17 cells (1.252 ± 0.134% vs. 2.567 ± 0.386%), serum IL-17A (49.42 ± 2.643 pg/ml vs. 66.75 ± 3.442 pg/ml) and Th17/Treg ratio (0.194 ± 0.025 vs. 0.439 ± 0.072) compared to baseline (P<0.01). The ICS/LABA+HDM-SCIT treatment group showed similar reduction in the percentage of Th17 cells (1.11 ± 0.114% vs. 2.654 ± 0.276%), serum IL-17A (49.23 ± 2.131 pg/ml vs. 66.41 ± 2.616 pg/ml) and the Th17/Treg ratio (0.133 ± 0.015 vs. 0.4193 ± 0.050) (P<0.01). ICS/LABA+HDM-SCIT treatment group demonstrated elevated Treg percentages (8.483 ± 0.408% vs. 6.549 ± 0.299%) and serum IL-10 levels (127.4 ± 4.423 pg/ml vs. 93.15 ± 4.046 pg/ml), resulting in a lower Th17/Treg ratio than the ICS/LABA group.

Conclusion

ICS/LABA treatment regulates Th17/Treg imbalance mainly by mitigating Th17-induced inflammation in asthma patients. The addition of SCIT further enhanced such effect by upregulating Treg cells.

Steroid-Refractory Gut Graft-Versus-Host Disease: What We Have Learned From Basic Immunology and Experimental Mouse Model

Intestinal graft-versus-host disease (Gut-GVHD) is one of the major causes of mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). While systemic glucocorticoids (GCs) comprise the first-line treatment option, the response rate for GCs varies from 30% to 50%. The prognosis for patients with steroid-refractory acute Gut-GVHD (SR-Gut-aGVHD) remains dismal. The mechanisms underlying steroid resistance are unclear, and apart from ruxolitinib, there are no approved treatments for SR-Gut-aGVHD. In this review, we provide an overview of the current biological understanding of experimental SR-Gut-aGVHD pathogenesis, the advanced technology that can be applied to the human SR-Gut-aGVHD studies, and the potential novel therapeutic options for patients with SR-Gut-aGVHD.

Physiological Convergence and Antagonism Between GR and PPARγ in Inflammation and Metabolism

Nuclear receptors (NRs) are transcription factors that modulate gene expression in a ligand-dependent manner. The ubiquitously expressed glucocorticoid receptor (GR) and peroxisome proliferator-activated receptor gamma (PPARγ) represent steroid (type I) and non-steroid (type II) classes of NRs, respectively. The diverse transcriptional and physiological outcomes of their activation are highly tissue-specific. For example, in subsets of immune cells, such as macrophages, the signaling of GR and PPARγ converges to elicit an anti-inflammatory phenotype; in contrast, in the adipose tissue, their signaling can lead to reciprocal metabolic outcomes. This review explores the cooperative and divergent outcomes of GR and PPARγ functions in different cell types and tissues, including immune cells, adipose tissue and the liver. Understanding the coordinated control of these NR pathways should advance studies in the field and potentially pave the way for developing new therapeutic approaches to exploit the GR:PPARγ crosstalk.

Mechanism of Rhinovirus Immunity and Asthma

The majority of asthma exacerbations in children are caused by Rhinovirus (RV), a positive sense single stranded RNA virus of the Picornavirus family. The host has developed virus defense mechanisms that are mediated by the upregulation of interferon-activated signaling. However, the virus evades the immune system by inducing immunosuppressive cytokines and surface molecules like programmed cell death protein 1 (PD-1) and its ligand (PD-L1) on immunocompetent cells. Initially, RV infects epithelial cells, which constitute a physiologic mucosal barrier. Upon virus entrance, the host cell immediately recognizes viral components like dsRNA, ssRNA, viral glycoproteins or CpG-DNA by host pattern recognition receptors (PRRs). Activation of toll like receptors (TLR) 3, 7 and 8 within the endosome and through MDA-5 and RIG-I in the cytosol leads to the production of interferon (IFN) type I and other antiviral agents. Every cell type expresses IFNAR1/IFNAR2 receptors thus allowing a generalized antiviral activity of IFN type I resulting in the inhibition of viral replication in infected cells and preventing viral spread to non-infected cells. Among immune evasion mechanisms of the virus, there is downregulation of IFN type I and its receptor as well as induction of the immunosuppressive cytokine TGF-β. TGF-β promotes viral replication and is associated with induction of the immunosuppression signature markers LAP3, IDO and PD-L1. This article reviews the recent advances on the regulation of interferon type I expression in association with RV infection in asthmatics and the immunosuppression induced by the virus.

Anti-inflammatory Roles of Glucocorticoids Are Mediated by Foxp3+ Regulatory T Cells via a miR-342-Dependent Mechanism

Glucocorticoids (GC) are the mainstay treatment option for inflammatory conditions. Despite the broad usage of GC, the mechanisms by which GC exerts its effects remain elusive. Here, utilizing murine autoimmune and allergic inflammation models, we report that Foxp3⁺ regulatory T (Treg) cells are irreplaceable GC target cells in vivo. Dexamethasone (Dex) administered in the absence of Treg cells completely lost its ability to control inflammation, and the lack of glucocorticoid receptor in Treg cells alone resulted in the loss of therapeutic ability of Dex. Mechanistically, Dex induced miR-342-3p specifically in Treg cells and miR-342-3p directly targeted the mTORC2 component, Rictor. Altering miRNA-342-3p or Rictor expression in Treg cells dysregulated metabolic programming in Treg cells, controlling their regulatory functions in vivo. Our results uncover a previously unknown contribution of Treg cells during glucocorticoid-mediated treatment of inflammation and the underlying mechanisms operated via the Dex-miR-342-Rictor axis.

Comparative Study of Immunomodulatory Agents to Induce Human T Regulatory (Treg) Cells: Preferential Treg-Stimulatory Effect of Prednisolone and Rapamycin

T regulatory (Treg) cells play a critical role in the maintenance of self-tolerance, as well as in inhibition of inflammation and exaggerated immune response against exogenous antigens. They develop in the thymus (tTreg cells) but also may be generated at the peripheral tissues, including tumor microenvironment (pTreg cells), or induced in vitro in the presence of transforming growth factor (TGF)-β (iTreg cells). Since tTreg cells constitute a minor fraction of peripheral blood lymphocytes in physiological conditions, an alternative way to obtain high number of functional Treg cells for therapeutic purposes is their generation in vitro from conventional T cells. In our studies, we compared effectiveness of several pharmacological agents with suggested immunomodulatory effects on Treg development (rapamycin, prednisolone, inosine pranobex, glatiramer acetate, sodium butyrate, and atorvastatin) to optimize Treg-inducing protocols. All but one (atorvastatin) immunomodulators augmented induction of polyclonal Treg cells in cultures. They were effective both in increasing the number of CD4⁺CD25^highFoxp3^high cells and Foxp3 expression. Rapamycin and prednisolone were found the most effective. Both drugs prolonged also phenotypic stability of Treg cells and induced fully active Treg cells in a functional assay. In the assay, prednisolone appeared superior versus rapamycin. The results, on the one hand, may be helpful in planning optimal protocols for generation of Treg cells for clinical application and, on the other hand, shed some light on mechanisms of the immunomodulatory activity of some tested agents observed in vivo.

The Possible Protective Role of Barley Seeds on the Spleen after Administration of Glucocorticoids in Adult Albino Rats: A Histological and Immunohistochemical Study

Background:

Glucocorticoids (GCs) are the main treatment strategy in many autoimmune disease and inflammatory diseases; however, they have immunosuppressive effect on many organs. The barley seeds contain many antioxidant compounds, which may improve the antioxidant status and related physiological functions. Our aim in this work is to evaluate the possible protective role of barley seeds on some immune cells in the spleen against immunosuppressive effect of GCs in adult albino rats.

Materials and Methods:

Forty-five adult albino rats were equally divided into 3 groups. Group I: normal vehicle control (n = 15), Group II: steroid-treated animals (n = 15), and Group III: steroid/barley-treated group (n = 15). Specimens from spleen were processed for light and electron microscopy.

Results:

In steroid-treated group, the histological changes in white and red pulp were in the form of loss of architecture and wide empty spaces among the cells. Most of the cells showed degenerative change, dilatation of blood sinusoids, and deposition of fibrinoid material among the cells of the RP. However, multiple lysosomal bodies were observed in both dendritic and macrophage cells. These changes are improved in steroid/barley-treated group in the form of increasing the number and size of the lymphatic follicles. Most of the splenic cells regained normal structure. Dendritic cell marker CD86 and macrophage marker CD68 expression are increased.

Conclusion:

Barley protects the spleen tissues from steroid-induced structural changes; this could be mediated through its antioxidant effects, so barely is recommended as a healthy diet in patients consuming steroids.

Multiple doses of adipose tissue-derived mesenchymal stromal cells induce immunosuppression in experimental asthma

In experimental house dust mite (HDM)‐induced allergic asthma, therapeutic administration of a single dose of adipose tissue‐derived mesenchymal stromal cells (MSCs) ameliorates lung inflammation but is unable to reverse remodeling. We hypothesized that multiple doses of MSCs might exert better therapeutic effects by reducing lung inflammation and remodeling but might also result in immunosuppressive effects in experimental asthma. HDM was administered intranasally in C57BL/6 mice. After the last HDM challenge, mice received two or three doses of MSCs (10⁵ cells per day) or saline intravenously. An additional cohort of mice received dexamethasone as a positive control for immunosuppression. Two and three doses of MSCs reduced lung inflammation, levels of interleukin (IL)‐4, IL‐13, and eotaxin; total leukocyte, CD4⁺ T‐cell, and eosinophil counts in bronchoalveolar lavage fluid; and total leukocyte counts in bone marrow, spleen, and mediastinal lymph nodes. Two and three doses of MSCs also reduced collagen fiber content and transforming growth factor‐β levels in lung tissue; however, the three‐dose regimen was more effective, and reduced these parameters to control levels, while also decreasing α‐actin content in lung tissue. Two and three doses of MSCs improved lung mechanics. Dexamethasone, two and three doses of MSCs similarly increased galectin levels, but only the three‐dose regimen increased CD39 levels in the thymus. Dexamethasone and the three‐dose, but not the two‐dose regimen, also increased levels of programmed death receptor‐1 and IL‐10, while reducing CD4⁺CD8^low cell percentage in the thymus. In conclusion, multiple doses of MSCs reduced lung inflammation and remodeling while causing immunosuppression in HDM‐induced allergic asthma.

Effects of Transportation and Relocation on Immunologic Measures in Cynomolgus Macaques (Macaca fascicularis)

NHP are a small, but critical, portion of the animals studied in research laboratories. Many NHP are imported or raised at one facility and subsequently moved to another facility for research purposes. To improve our understanding of the effects of transportation and relocation on the NHP immune system, to minimize potential confounds associated with relocation, and to maximize study validity, we examined the phenotype and function of PBMC in cynomolgus macaques (Macaca fascicularis) that were transported approximately 200 miles by road from one facility to another. We evaluated the phenotype of lymphocyte subsets through flow cytometry, mitogen-specific immune responses of PBMC in vitro, and plasma levels of circulating cytokines before transportation, at approximately 24 h after arrival (day 2), and after 30 d of acclimation. Analyses of blood samples revealed that the CD3+ and CD4+ T-cell counts increased significantly, whereas NK+, NKT, and CD14+ CD16+ nonclassical monocyte subsets were decreased significantly on day 2 after relocation compared with baseline. We also noted significantly increased immune cell function as indicated by mitogen-specific proliferative responses and by IFNγ levels on day 2 compared with baseline. After 30 d of acclimation, peripheral blood CD4+ T-cells and monocyte counts were higher than baseline, whereas B-cell numbers were lower. The mitogen-induced responses to LPS and IFNγ production after stimulation with pokeweed mitogen or phytohemagglutinin remained significantly different from baseline. In conclusion, the effects of transportation and relocation on immune parameters in cynomolgus monkeys are significant and do not fully return to baseline values even after 30 d of acclimation.

Context-Dependent Effect of Glucocorticoids on the Proliferation, Differentiation, and Apoptosis of Regulatory T Cells: A Review of the Empirical Evidence and Clinical Applications

Glucocorticoids (GCs) are widely used to treat several diseases because of their powerful anti-inflammatory and immunomodulatory effects on immune cells and non-lymphoid tissues. The effects of GCs on T cells are the most relevant in this regard. In this review, we analyze how GCs modulate the survival, maturation, and differentiation of regulatory T (Treg) cell subsets into both murine models and humans. In this way, GCs change the Treg cell number with an impact on the mid-term and long-term efficacy of GC treatment. In vitro studies suggest that the GC-dependent expansion of Treg cells is relevant when they are activated. In agreement with this observation, the GC treatment of patients with established autoimmune, allergic, or (auto)inflammatory diseases causes an expansion of Treg cells. An exception to this appears to be the local GC treatment of psoriatic lesions. Moreover, the effects on Treg number in patients with multiple sclerosis are uncertain. The effects of GCs on Treg cell number in healthy/diseased subjects treated with or exposed to allergens/antigens appear to be context-dependent. Considering the relevance of this effect in the maturation of the immune system (tolerogenic response to antigens), the success of vaccination (including desensitization), and the tolerance to xenografts, the findings must be considered when planning GC treatment.

The effect of methylprednisolone prophylaxis on inflammatory monocyte subsets and suppressive regulatory T cells of patients undergoing cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass (CPB) during open-heart surgery triggers an inflammatory response that can cause significant morbidity and mortality. Human monocytes and regulatory T (Treg) cells are phenotypically and functionally heterogeneous and have been shown to play a significant role in the inflammatory dysfunction triggered by CPB. Glucocorticoids (GCs) have been widely administered for decades in patients undergoing CPB to reduce this inflammatory response. However, it has not been clearly established how routine prophylactic administration of glucocorticoids (GCs) affects monocyte and Treg subsets.

METHODS

Thirty-six patient who underwent heart surgery with CPB were randomly assigned to a methylprednisolone group (MG, N = 18; 500 mg in the CPB priming) and a non-methylprednisolone group (NMG, N = 18). The circulating monocyte and Treg subsets were analyzed by flow cytometry.

RESULTS

The MG and NMG groups had comparable percentages of monocyte subsets and similar expression levels of HLA-DR, CD86, CD64 and toll-like receptor 4 (TLR4). Remarkably, methylprednisolone increased the percentage of CD4+CD25+ Treg cells among CD4+ T cells in patients undergoing CPB, but did not increase the proportion of suppressive Treg cells, either resting or activated, in these patients undergoing CPB.

CONCLUSIONS

Our results showed that prophylactic administration of methylprednisolone neither decreased the percentages and counts of inflammatory monocyte subsets nor did it induce the expansion of suppressive Treg cells in patients undergoing CPB. These results clarified the effects of GCs on cell-mediated immune responses and provided additional evidence in practice.

TRIAL REGISTRATION

Clinicaltrials.gov : NCT01296074. Registered 14 February 2011.

Maternal Separation as Early-Life Stress Causes Enhanced Allergic Airway Responses by Inhibiting Respiratory Tolerance in Mice

Epidemiologic studies indicate that exposure to psychosocial stress in early childhood is a risk factor of adult-onset asthma, but the mechanisms of this relationship are poorly understood. Therefore, we examined whether early-life stress increases susceptibility to adult-onset asthma by inhibiting the development of respiratory tolerance. Neonatal BALB/c female mice were aerosolized with ovalbumin (OVA) to induce immune tolerance prior to immune sensitization with an intraperitoneal injection of OVA and the adjuvant aluminum hydroxide. Maternal separation (MS) was applied as an early-life stressor during the induction phase of immune tolerance. The mice were challenged with OVA aerosol in adulthood, and allergic airway responses were evaluated, including airway hyper-responsiveness to inhaled methacholine, inflammatory cell infiltration, bronchoalveolar lavage fluid levels of interleukin (IL)-4, IL-5, and IL-13, and serum OVA-specific IgE. We then evaluated the effects of MS on the development of regulatory T (Treg) cells in bronchial lymph nodes (BLN) and on splenocyte proliferation and cytokine expression. In mice that underwent MS and OVA tolerization, the allergic airway responses and OVA-induced proliferation and IL-4 expression of splenocytes were significantly enhanced. Furthermore, exposure to MS was associated with a lower number of Treg cells in the BLN. These findings suggest that exposure to early-life stress prevents the acquisition of respiratory tolerance to inhaled antigen due to insufficient Treg cell development, resulting in Th2-biased sensitization and asthma onset. We provide the evidence for inhibitory effects of early-life stress on immune tolerance. The present findings may help to clarify the pathogenesis of adult-onset asthma.

Glucocorticoid hormone differentially modulates the in vitro expansion and cytokine profile of thymic and splenic Treg cells

OBJECTIVE

Functional disturbances in regulatory T cells (Treg) have been described in autoimmune diseases, and their potential therapeutic use is intensively studied. Our goal was to investigate the influence of glucocorticoid hormone on the in vitro differentiation of Treg cells from thymic and splenic CD4⁺ T cells under different conditions to establish methods for generating stable and functionally suppressive iTregs for future use in adoptive transfer experiments.

METHODS

Thymic and splenic CD4⁺ T lymphocytes were isolated from 3 to 4 week-old control and in vivo dexamethasone (DX) pretreated BALB/c mice using magnetic bead negative selection, followed by CD25 positive selection. The cells were cultured with anti-CD3/CD28 beads and IL-2 in the presence or absence of TGFβ and/or DX for 3-6 days. Multiparametric flow cytometry was performed using CD4, CD25, CD8, TGFβ (LAP) cell surface and Foxp3, IL-4, IL-10, IL-17 and IFNγ intracellular staining. Quantitative RT-PCR was performed to measure IL-10, TGFβ cytokine and Foxp3 mRNA levels.

RESULTS

Differentiation of thymus-derived CD4⁺ cells in vitro into iTreg cells was most effective (24-25%) when anti-CD3/CD28 beads, IL-2, and TGFβ were present. Splenic CD4⁺ T cell expansion under same conditions resulted in a higher (44-45%) iTreg cell ratio that further increased (up to 50% Treg) in the presence of DX. Elevated immunosuppressive cytokine (IL-10 and TGFβ) production by iTregs could be measured both at protein and mRNA levels without elevation of Th1/Th2 or Th17 cytokine production. We got the highest iTreg ratio (74%) and TGFβ production when CD4⁺CD25⁺ splenic T cells were stimulated in the presence of TGFβ. In vivo 4 days DX pretreatment resulted in enhanced in vitro expansion and Foxp3 expression of thymus-derived iTregs and decreased differentiation of spleen-derived iTreg cells. In these Tregs the relative expression of IL-10 mRNA significantly decreased under all in vitro stimulation conditions, while TGFβ mRNA level did not change.

CONCLUSION

DX promotes the expansion of thymic and splenic Treg cells, and enhances Foxp3⁺ expression and the production of immunosuppressive cytokines IL-10 and TGFβ in vitro. In vivo pretreatment of mice with DX inhibited the immunosuppressive cytokine production of in vitro differentiated Treg cells. We hypothesize that patients receiving GC therapy may need special attention prior to in vitro expansion and transplantation of Treg cells.

Serum from Asthmatic Mice Potentiates the Therapeutic Effects of Mesenchymal Stromal Cells in Experimental Allergic Asthma

Asthma is a chronic inflammatory disease characterized by airway inflammation and remodeling, which can lead to progressive decline of lung function. Although mesenchymal stromal cells (MSCs) have shown beneficial immunomodulatory properties in preclinical models of allergic asthma, effects on airway remodeling have been limited. Mounting evidence suggests that prior exposure of MSCs to specific inflammatory stimuli or environments can enhance their immunomodulatory properties. Therefore, we investigated whether stimulating MSCs with bronchoalveolar lavage fluid (BALF) or serum from asthmatic mice could potentiate their therapeutic properties in experimental asthma. In a house dust mite (HDM) extract asthma model in mice, unstimulated, asthmatic BALF‐stimulated, or asthmatic serum‐stimulated MSCs were administered intratracheally 24 hours after the final HDM challenge. Lung mechanics and histology; BALF protein, cellularity, and biomarker levels; and lymph‐node and bone marrow cellularity were assessed. Compared with unstimulated or BALF‐stimulated MSCs, serum‐stimulated MSCs further reduced BALF levels of interleukin (IL)‐4, IL‐13, and eotaxin, total and differential cellularity in BALF, bone marrow and lymph nodes, and collagen fiber content, while increasing BALF IL‐10 levels and improving lung function. Serum stimulation led to higher MSC apoptosis, expression of various mediators (transforming growth factor‐β, interferon‐γ, IL‐10, tumor necrosis factor‐α‐stimulated gene 6 protein, indoleamine 2,3‐dioxygenase‐1, and IL‐1 receptor antagonist), and polarization of macrophages to M2 phenotype. In conclusion, asthmatic serum may be a novel strategy to potentiate therapeutic effects of MSCs in experimental asthma, leading to further reductions in both inflammation and remodeling than can be achieved with unstimulated MSCs. stem cells translational medicine2019;8:301&312

Impact of one versus two doses of mesenchymal stromal cells on lung and cardiovascular repair in experimental emphysema

Background

A single administration of mesenchymal stromal cells (MSCs) has been shown to reduce lung inflammation in experimental elastase-induced emphysema; however, effects were limited in terms of lung-tissue repair and cardiac function improvement. We hypothesized that two doses of MSCs could induce further lung and cardiovascular repair by mitigating inflammation and remodeling in a model of emphysema induced by multiple elastase instillations. We aimed to comparatively investigate the effects of one versus two doses of MSCs, administered 1 week apart, in a murine model of elastase-induced emphysema.

Methods

C57BL/6 mice were randomly divided into control (CTRL) and emphysema (E) groups. Mice in the E group received porcine pancreatic elastase (0.2 IU, 50 μL) intratracheally once weekly for four consecutive weeks; the CTRL animals received sterile saline (50 μL) using the same protocol. Three hours after the last instillation, the E group was further randomized to receive either saline (SAL) or murine MSCs (10⁵ cells) intratracheally, in one or two doses (1 week apart). Fourteen days later, mice were euthanized, and all data analyzed.

Results

Both one and two doses of MSCs improved lung mechanics, reducing keratinocyte-derived chemokine and transforming growth factor-β levels in lung homogenates, total cell and macrophage counts in bronchoalveolar lavage fluid (BALF), and collagen fiber content in airways and blood vessels, as well as increasing vascular endothelial growth factor in lung homogenates and elastic fiber content in lung parenchyma. However, only the two-dose group exhibited reductions in tumor necrosis factor-α in lung tissue, BALF neutrophil and lymphocyte count, thymus weight, and total cellularity, as well as CD8⁺ cell counts and cervical lymph node CD4⁺ and CD8⁺ T cell counts, as well as further increased elastic fiber content in the lung parenchyma and reduced severity of pulmonary arterial hypertension.

Conclusions

Two doses of MSCs enhanced lung repair and improvement in cardiac function, while inducing T cell immunosuppression, mainly of CD8⁺ cells, in elastase-induced emphysema.

Increased Susceptibility to Allergic Asthma with the Impairment of Respiratory Tolerance Caused by Psychological Stress

BACKGROUND

Bronchial asthma is characterized by type 2 T helper (Th2) cell inflammation, essentially due to a breakdown of immune tolerance to harmless environmental allergens. Etiologically, experiences of psychological stress can be associated with a heightened prevalence of asthma. However, the mechanisms underlying stress-related asthma development are unclear. In this study, we examined whether psychological stress increases susceptibility to allergic asthma by downregulating immune tolerance.

METHODS

Female BALB/c mice were sensitized with ovalbumin/alum, followed by ovalbumin inhalation. Ovalbumin inhalation induced immune tolerance before sensitization occurred. Some mice were exposed to restraint stress during tolerance induction or sensitization. Asthma development was evaluated by airway responsiveness, inflammation, cytokine expression, and IgE synthesis. Sensitization was evaluated by measuring proliferation and cytokine production by splenocytes. The effects of stress exposure on the numbers and functions of dendritic cells and regulatory T (Treg) cells in bronchial lymph nodes and spleens were evaluated. To investigate the role of endogenous glucocorticoid in inhibiting immune tolerance after stress exposure, we examined the effects of (i) a glucocorticoid-receptor antagonist administered prior to stress exposure, and (ii) exogenous gluco-corticoid (instead of stress exposure).

RESULTS

Asthmatic responses and Th2-biased sensitization, which were suppressed in tolerized mice, re-emerged in tolerized mice stressed during tolerance induction in association with decreased tolerogenic dendritic and Treg cell numbers. The effects of stress exposure on tolerized mice were abolished by administering a glucocorticoid-receptor antagonist and reproduced by administering exogenous glucocorticoid without stress.

CONCLUSIONS

Our findings suggested that psychological stress can potentially increase allergic asthma susceptibility by inhibiting immune tolerance.

Eicosapentaenoic Acid Enhances the Effects of Mesenchymal Stromal Cell Therapy in Experimental Allergic Asthma

Asthma is characterized by chronic lung inflammation and airway hyperresponsiveness. Despite recent advances in the understanding of its pathophysiology, asthma remains a major public health problem and, at present, there are no effective interventions capable of reversing airway remodeling. Mesenchymal stromal cell (MSC)-based therapy mitigates lung inflammation in experimental allergic asthma; however, its ability to reduce airway remodeling is limited. We aimed to investigate whether pre-treatment with eicosapentaenoic acid (EPA) potentiates the therapeutic properties of MSCs in experimental allergic asthma. Seventy-two C57BL/6 mice were used. House dust mite (HDM) extract was intranasally administered to induce severe allergic asthma in mice. Unstimulated or EPA-stimulated MSCs were administered intratracheally 24 h after final HDM challenge. Lung mechanics, histology, protein levels of biomarkers, and cellularity in bronchoalveolar lavage fluid (BALF), thymus, lymph nodes, and bone marrow were analyzed. Furthermore, the effects of EPA on lipid body formation and secretion of resolvin-D₁ (RvD₁), prostaglandin E₂ (PGE₂), interleukin (IL)-10, and transforming growth factor (TGF)-β1 by MSCs were evaluated in vitro. EPA-stimulated MSCs, compared to unstimulated MSCs, yielded greater therapeutic effects by further reducing bronchoconstriction, alveolar collapse, total cell counts (in BALF, bone marrow, and lymph nodes), and collagen fiber content in airways, while increasing IL-10 levels in BALF and M2 macrophage counts in lungs. In conclusion, EPA potentiated MSC-based therapy in experimental allergic asthma, leading to increased secretion of pro-resolution and anti-inflammatory mediators (RvD₁, PGE₂, IL-10, and TGF-β), modulation of macrophages toward an anti-inflammatory phenotype, and reduction in the remodeling process. Taken together, these modifications may explain the greater improvement in lung mechanics obtained. This may be a promising novel strategy to potentiate MSCs effects.

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.

Progressive increase in allergen concentration abrogates immune tolerance in ovalbumin-induced murine model of chronic asthma

Persistent inflammation and remodeling of airways are the major hallmarks of asthma. Though airway inflammation diminishes in ovalbumin (OVA)-based mouse model of chronic asthma owing to immune-tolerance linked with repeated allergen exposure, which limits the application of the disease model. Accordingly, the present study was designed to develop a murine model of chronic asthma which presents persistent airway inflammation coupled with remodeling traits. Herein, OVA-sensitized BALB/c mice were challenged with increasing (modified protocol) or constant concentration (conventional protocol) of the allergen for 6 weeks; 3 times/week. The results, indeed, revealed that mice subjected to modified protocol demonstrate an improved response to the allergen as reflected by the significant increase in inflammatory cells particularly, eosinophils in bronchoalveolar lavage fluid compared to conventional protocol. Moreover, the expression of Th2 cytokines and their responsible transcription factors (GATA-3 and STAT-6) was markedly enhanced in lungs. The increase in inflammation was further accompanied by a marked increase in mucus production, collagen deposition, and the expression of allied factors (Muc5ac, Col1α1, and α-SMA). Interestingly, pre-treatment of dexamethasone, a corticosteroid (0.5 mg/kg b.wt., i.p.), suppressed the allergen-induced airway inflammation and mucus production without altering collagen deposition. Failure of dexamethasone seems to be related to their ineffectiveness to modulate the expression of TGF-β, MMP-9, COL1α1, and α-SMA. Overall, our results strongly suggest that mice underwent modified chronic protocol bears more resemblance with asthmatics as it imitates persistent airway inflammation allied with steroid-refractory remodeling traits; hence, may be useful for the evaluation of new/alternative drugs in steroid-refractory asthmatic conditions.

The number and function of T regulatory cells in obese atopic female asthmatics

BACKGROUND

Mechanisms underlying the association between asthma and obesity remain poorly understood. Obesity appears to be a risk factor for asthma, and obese asthmatics fare poorly compared to lean asthmatics.

OBJECTIVES

To explore the possibility that reduced regulatory T cell (Treg) number and function contribute to the obesity-asthma association. We concentrated on obese females with childhood-onset asthma, since Treg may be involved in this phenotype.

METHODS

We recruited 64 women (ages 18-50) into four groups: lean (BMI 18-25 kg/m²) controls (n = 17) and asthmatics (n = 13), and obese (BMI ≥ 35 kg/m²) controls (n = 17) and asthmatics (n = 17). Asthmatics had atopy and childhood-diagnosed asthma. We assessed lung function, asthma control and quality of life. Peripheral blood CD4+/CD25+/FoxP3+ Treg cells were identified and counted by flow cytometry and expressed as % total CD4+ T cells. We assessed Treg cell function by the ability of CD4+/CD25+ Treg cells to suppress autologous CD4+/CD25- responder T cell (Tresp) proliferation and measured as % suppression of Tresp cell proliferation.

RESULTS

Obese asthmatics had worse lung function, asthma control, and quality of life compared to lean asthmatics. Compared to lean or obese control groups, the number of Treg cells in the obese asthmatics was approximately 1.58- or 1.73-fold higher. The ability of Treg cells from obese-asthmatics to suppress Tresp cell proliferation was reduced.

CONCLUSIONS

Obese, atopic women with childhood diagnosed asthma demonstrate increased Treg cell number and mildly decreased Treg cell function. Our data do not support the view that reduced Treg cell number contributes to this obese-asthma phenotype.

The interplay between neuroendocrine activity and psychological stress-induced exacerbation of allergic asthma

Psychological stress is recognized as a key factor in the exacerbation of allergic asthma, whereby brain responses to stress act as immunomodulators for asthma. In particular, stress-induced enhanced type 2 T-helper (Th2)-type lung inflammation is strongly associated with asthma pathogenesis. Psychological stress leads to eosinophilic airway inflammation through activation of the hypothalamic-pituitary-adrenal pathway and autonomic nervous system. This is followed by the secretion of stress hormones into the blood, including glucocorticoids, epinephrine, and norepinephrine, which enhance Th2 and type 17 T-helper (Th17)-type asthma profiles in humans and rodents. Recent evidence has shown that a defect of the μ-opioid receptor in the brain along with a defect of the peripheral glucocorticoid receptor signaling completely disrupted stress-induced airway inflammation in mice. This suggests that the stress response facilitates events in the central nervous and endocrine systems, thus exacerbating asthma. In this review, we outline the recent findings on the interplay between stress and neuroendocrine activities followed by stress-induced enhanced Th2 and Th17 immune responses and attenuated regulatory T (Treg) cell responses that are closely linked with asthma exacerbation. We will place a special focus on our own data that has emphasized the continuity from central sensing of psychological stress to enhanced eosinophilic airway inflammation. The mechanism that modulates psychological stress-induced exacerbation of allergic asthma through neuroendocrine activities is thought to involve a series of consecutive pathological events from the brain to the lung, which implies there to be a "neuropsychiatry phenotype" in asthma.

Regulatory and Mechanistic Actions of Glucocorticoids on T and Inflammatory Cells

Glucocorticoids (GCs) play an important role in regulating the inflammatory and immune response and have been used since decades to treat various inflammatory and autoimmune disorders. Fine-tuning the glucocorticoid receptor (GR) activity is instrumental in the search for novel therapeutic strategies aimed to reduce pathological signaling and restoring homeostasis. Despite the primary anti-inflammatory actions of GCs, there are studies suggesting that under certain conditions GCs may also exert pro-inflammatory responses. For these reasons the understanding of the GR basic mechanisms of action on different immune cells in the periphery (e.g., macrophages, dendritic cells, neutrophils, and T cells) and in the brain (microglia) contexts, that we review in this chapter, is a continuous matter of interest and may reveal novel therapeutic targets for the treatment of immune and inflammatory response.

Therapeutic administration of bone marrow-derived mesenchymal stromal cells reduces airway inflammation without up-regulating Tregs in experimental asthma

BACKGROUND

Prophylactic administration of mesenchymal stromal cells (MSCs) derived from adipose (AD-MSC) and bone marrow tissue (BM-MSC) in ovalbumin-induced asthma hinders inflammation in a Treg-dependent manner. It is uncertain whether MSCs act through Tregs when inflammation is already established in asthma induced by a clinically relevant allergen.

OBJECTIVE

Evaluate the effect of therapeutic administration of MSCs on inflammation and Treg cells in house dust mite (HDM)-induced asthma.

METHODS

BM-MSCs and AD-MSCs were administered intratracheally to C57BL/6 mice 1 day after the last HDM challenge. Lung function, remodelling and parenchymal inflammation were assayed 3 or 7 days after MSCs treatment, through invasive plethysmography and histology, respectively. Bronchoalveolar lavage fluid (BALF) and mediastinal lymph nodes (mLNs) were assessed regarding the inflammatory profile by flow cytometry, ELISA and qRT-PCR. MSCs were studied regarding their potential to induce Treg cells from primed and unprimed lymphocytes in vitro.

RESULTS

BM-MSCs, but not AD-MSCs, reduced lung influx of eosinophils and B cells and increased IL-10 levels in HDM-challenged mice. Neither BM-MSCs nor AD-MSCs reduced lung parenchymal inflammation, airway hyperresponsiveness or mucus hypersecretion. BM-MSCs and AD-MSCs did not up-regulate Treg cell counts within the airways and mLNs, but BM-MSCs decreased the pro-inflammatory profile of alveolar macrophages. Co-culture of BM-MSCs and AD-MSCs with allergen-stimulated lymphocytes reduced Treg cell counts in a cell-to-cell contact-independent manner, although co-culture of both MSCs with unprimed lymphocytes up-regulated Treg cell counts.

CONCLUSIONS

MSCs therapeutically administered exert anti-inflammatory effects in the airway of HDM-challenged mice, but do not ameliorate lung function or remodelling. Although MSC pre-treatment can increase Treg cell numbers, it is highly unlikely that the MSCs will induce Treg cell expansion when lymphocytes are allergenically primed in an established lung inflammation.

Regulatory T cells in multiple sclerosis and myasthenia gravis

Multiple sclerosis (MS) is a chronic debilitating disease of the central nervous system primarily mediated by T lymphocytes with specificity to neuronal antigens in genetically susceptible individuals. On the other hand, myasthenia gravis (MG) primarily involves destruction of the neuromuscular junction by antibodies specific to the acetylcholine receptor. Both autoimmune diseases are thought to result from loss of self-tolerance, which allows for the development and function of autoreactive lymphocytes. Although the mechanisms underlying compromised self-tolerance in these and other autoimmune diseases have not been fully elucidated, one possibility is numerical, functional, and/or migratory deficits in T regulatory cells (Tregs). Tregs are thought to play a critical role in the maintenance of peripheral immune tolerance. It is believed that Tregs function by suppressing the effector CD4+ T cell subsets that mediate autoimmune responses. Dysregulation of suppressive and migratory markers on Tregs have been linked to the pathogenesis of both MS and MG. For example, genetic abnormalities have been found in Treg suppressive markers CTLA-4 and CD25, while others have shown a decreased expression of FoxP3 and IL-10. Furthermore, elevated levels of pro-inflammatory cytokines such as IL-6, IL-17, and IFN-γ secreted by T effectors have been noted in MS and MG patients. This review provides several strategies of treatment which have been shown to be effective or are proposed as potential therapies to restore the function of various Treg subsets including Tr1, iTr35, nTregs, and iTregs. Strategies focusing on enhancing the Treg function find importance in cytokines TGF-β, IDO, interleukins 10, 27, and 35, and ligands Jagged-1 and OX40L. Likewise, strategies which affect Treg migration involve chemokines CCL17 and CXCL11. In pre-clinical animal models of experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune myasthenia gravis (EAMG), several strategies have been shown to ameliorate the disease and thus appear promising for treating patients with MS or MG.

Effect of inhaled and systemic glucocorticoid treatment on CD4+ regulatory and effector T cells in a mouse model of allergic asthma

To achieve a better understanding of mechanisms underlying the anti-asthmatic action of inhaled and systemic glucocorticoids (GCs) and to provide more data regarding the risk of a negative effect of inhaled GCs on CD4⁺ T cells, a study was conducted on the effect of ciclesonide and methylprednisolone on CD4⁺ effector (Teff), regulatory (Treg) and resting (Trest) T cells within respiratory and extra-respiratory tissues in a mouse model of allergic asthma. The study indicated that one, and possibly a key mechanism, underlying the anti-asthmatic action of inhaled and systemic GCs is the prevention of the activation and clonal expansion of CD4⁺ Teff cells in the mediastinal lymph nodes (MLNs), which consequently prevents infiltration of the lungs with CD4⁺ Teff cells. The beneficial effects of GCs in asthma treatment were not mediated through increased recruitment of Treg cells into the MLNs and lungs and/or local generation of Treg cells. The results demonstrated that inhaled and systemic GCs induced comparable depletion of normal CD4⁺ Teff, Trest and Treg cells in the MLNs, head and neck lymph nodes and peripheral blood. Furthermore, inhaled, but not systemic GC therapy, led to the loss of these cells in the lungs. Thus, the study suggests that inhaled GC therapy may not be safer at all than systemic one with respect to the adverse effect on CD4⁺ T cells present within and outside the respiratory tract. Moreover, administration of inhaled GCs can produce negative effects on lung-residing CD4⁺ T cells.

Short-term intratracheal use of PEG-modified IL-2 and glucocorticoid persistently alleviates asthma in a mouse model

Regulatory T (Treg) cells play an important role in allergic airway diseases, and upregulation of Treg cells is a potential therapeutic strategy for asthma. In this study, we show that short-term intratracheal use of IL-2 combined with glucocorticoid alleviates antigen-induced airway inflammation and reduces airway hyperresponsiveness by expanding antigen-nonspecific Treg cells, with a decrease in T helper 2 (Th2) cells and Th2-associated cytokines. We also designed a long-acting polyethylene glycol (PEG)-modified IL-2 and demonstrated that the optimal dosage form is IL-2(PEG) plus budesonide, which can upregulate Treg cells and ameliorate asthma at a lower dose. The therapeutic effect was faster than treatment with dexamethasone and was effective at a low dose suitable for humans that could last for at least 6 weeks. This study unveils a new therapeutic regimen and suggests that such endogenous Treg therapy could be a useful tool to persistently alleviate asthma.

A gradient of glucocorticoid sensitivity among helper T cell cytokines

Helper T (Th) cells secret specific cytokines that promote immune responses whereas glucocorticoids limit the extent of immune responses by inhibiting cytokine secretion and other functions of Th cells. However, glucocorticoid resistance develops in subgroups of patients with Th cell-driven diseases such as asthma and Crohn's disease. Recent evidence supports that Th1, Th2, and Th17 cells have distinct glucocorticoid sensitivity. Th1 cells are sensitive to glucocorticoid-induced apoptosis and cytokine suppression while Th2 cells are sensitive to the latter but not the former and Th17 cells are resistant to both. This gradient of glucocorticoid sensitivity of Th cells corresponds to the glucocorticoid sensitivity of the diseases they underlie. We identify the mechanisms contributing to distinct glucocorticoid sensitivity of Th cells and their cytokines in the literature, as this information is useful to improve treatment strategies for glucocorticoid resistant immunological disorders.

Allergic lung inflammation promotes atherosclerosis in apolipoprotein E-deficient mice

Inflammation drives asthma and atherosclerosis. Clinical studies suggest that asthmatic patients have a high risk of atherosclerosis. Yet this hypothesis remains uncertain, given that Th2 imbalance causes asthma whereas Th1 immunity promotes atherosclerosis. In this study, chronic allergic lung inflammation (ALI) was induced in mice by ovalbumin sensitization and challenge. Acute ALI was induced in mice by ovalbumin and aluminum sensitization and ovalbumin challenge. Atherosclerosis was produced in apolipoprotein E-deficient (Apoe(-/-)) mice with a Western diet. When chronic ALI and atherosclerosis were produced simultaneously, ALI increased atherosclerotic lesion size, lesion inflammatory cell content, elastin fragmentation, smooth muscle cell (SMC) loss, lesion cell proliferation, and apoptosis. Production of acute ALI before atherogenesis did not affect lesion size, but increased atherosclerotic lesion CD4(+) T cells, lesion SMC loss, angiogenesis, and apoptosis. Production of acute ALI after atherogenesis also did not change atherosclerotic lesion area, but increased lesion elastin fragmentation, cell proliferation, and apoptosis. In mice with chronic ALI and diet-induced atherosclerosis, daily inhalation of a mast cell inhibitor or corticosteroid significantly reduced atherosclerotic lesion T-cell and mast cell contents, SMC loss, angiogenesis, and cell proliferation and apoptosis, although these drugs did not affect lesion area, compared with those that received vehicle treatment. In conclusion, both chronic and acute ALI promote atherogenesis or aortic lesion pathology, regardless whether ALI occurred before, after, or at the same time as atherogenesis. Antiasthmatic medication can efficiently mitigate atherosclerotic lesion pathology.

IκB kinase β inhibitor, IMD-0354, prevents allergic asthma in a mouse model through inhibition of CD4(+) effector T cell responses in the lung-draining mediastinal lymph nodes

IκB kinase (IKK) is important for nuclear factor (NF)-κB activation under inflammatory conditions. It has been demonstrated that IMD-0354, i.e. a selective inhibitor of IKKβ, inhibited allergic inflammation in a mouse model of ovalbumin (OVA)-induced asthma. The present study attempts to shed light on the involvement of CD4(+) effector (Teff) and regulatory (Treg) T cells in the anti-asthmatic action of IMD-0354. The animals were divided into three groups: vehicle treated, PBS-sensitized/challenged mice (PBS group); vehicle treated, OVA-sensitized/challenged mice (OVA group); and IMD-0354-treated, OVA-sensitized/challenged mice. The analyzed parameters included the absolute counts of Treg cells (Foxp3(+)CD25(+)CD4(+)), activated Teff cells (Foxp3(-)CD25(+)CD4(+)) and resting T cells (CD25(-)CD4(+)) in the mediastinal lymph nodes (MLNs), lungs and peripheral blood. Moreover, lung histopathology was performed to evaluate lung inflammation. It was found that the absolute number of cells in all studied subsets was considerably increased in the MLNs and lungs of mice from OVA group as compared to PBS group. All of these effects were fully prevented by treatment with IMD-0354. Histopathological examination showed that treatment with IMD-0354 protected the lungs from OVA-induced allergic airway inflammation. Our results indicate that IMD-0354 exerts anti-asthmatic action, at least partially, by blocking the activation and clonal expansion of CD4(+) Teff cells in the MLNs, which, consequently, prevents infiltration of the lungs with activated CD4(+) Teff cells. The beneficial effects of IMD-0354 in a mouse model of asthma are not mediated through increased recruitment of Treg cells into the MLNs and lungs and/or local generation of inducible Treg cells.