Respiratory tolerance is inhibited by the administration of corticosteroids

Time-dependent dual beneficial modulation of interferon-γ, interleukin 5, and Treg cytokines in asthma patient peripheral blood mononuclear cells by ganoderic acid B

Th2 cytokines play a dominant role in the pathogenesis of allergic asthma. Interferon gamma (IFN-γ), a Th1 cytokine, links to therapeutic mechanisms of allergic asthma. Interleukin (IL)-10, a regulatory cytokine, is involved in the induction of immune tolerance. We previously demonstrated that Anti-Asthma Simplified Herbal Medicine Intervention (ASHMI) suppressed Th2 and increased IFN-γ in patients with asthma and in animal models, but its bioactive compound is unknown. Ganoderic acid beta (GAB) was isolated from Ganoderma lucidum (one herb in ASHMI). Human peripheral blood mononuclear cells (PBMCs) from adult patients with asthma were cultured with GAB or dexamethasone (Dex) in the presence of environmental allergens. The cytokine levels of IL-10, IFN-γ, IL-5, transcription factors T-bet, Foxp-3, and GATA3 were measured. Following 3-day culture, GAB, but not Dex, significantly increased IL-10 and IFN-γ levels by allergic patients' PBMCs. Following 6-day treatment, GAB inhibited IL-5 production, but IL-10 and IFN-γ remained high. Dex suppressed production of all three cytokines. GAB suppressed GATA3 and maintained Foxp-3 and T-bet gene expression, while Dex significantly suppressed GATA3 and T-bet expression. GAB simultaneously increased IL-10, IFN-γ associated with induction of T-bet and Foxp3, while suppressing IL-5, which was associated with suppression of GATA3, demonstrating unique beneficial cytokine modulatory effect, which distinguishes from Dex's overall suppression.

Sophora flavescens Alkaloids and Corticosteroid Synergistically Augment IL-10/IL-5 Ratio with Foxp3-Gene-Epigenetic Modification in Asthma PBMCs

Background

It has been demonstrated that ASHMI (antiasthma-simplified herbal medicine intervention) can improve airway function and reduce inflammation in human asthmatic patients with high safety and tolerability. In addition, ASHMI significantly suppresses Th2 cytokine production and increases Th1 cytokine production in treating asthma.

Objective

Allergic asthma is associated with dysregulation of cytokines. We focused on IL-5 and IL-10 as signature Th2 and Treg cytokines to characterize ASHMI immunomodulatory components.

Methods

The effects of ASHMI and individual herbal constituents on IL-5 and IL-10 production by PBMCs from asthmatic subjects were determined ex vivo. Sophora flavescens (SF)-F2, containing alkaloid compounds, effects on PBMC IL-10 and IL-5 production in the presence or absence of dexamethasone (Dex), and on DNA methylation levels at the foxp3 gene promoter were determined.

Results

The ratio of anti-CD3/CD28 stimulated IL-10/IL-5 production by PBMCs from asthmatic subjects was significantly reduced compared to healthy subjects. In PBMCs from asthmatic subjects, ASHMI significantly reduced IL-5 production and increased IL-10 secretion in a dose-dependent manner (p < 0.05–0.01). SF-F2 was most effective in increasing IL-10, whereas SF-F4 (flavonoid compounds) was most effective in suppressing IL-5 production. Dex-treated PBMCs from asthma subjects showed a trend of increasing ratio of IL-10/IL-5 while demonstrating reduced levels in both IL-5 and IL-10 (p < 0.05). Co-culture with Dex and SF-F2 significantly prevented Dex suppression of IL-10, while retained Dex-suppression of IL-5 production, and increased IL-10/IL-5 ratio by Dex. Co-culture with SF-F2 and Dex significantly reduced DNA methylation levels at the foxp3 gene promoter at CpG⁻¹²⁶.

Conclusion

The SF alkaloid-rich fraction may be responsible for ASHMI induction of IL-10 production by PBMCs and plays a synergistic effect with Dex for augmenting IL-10/IL-5 ratio.

Regulatory T cells are less sensitive to glucocorticoid hormone induced apoptosis than CD4+ T cells

Earlier we have reported that thymic regulatory T cells (Treg) are resistant to in vivo glucocorticoid hormone (GC)-induced apoptosis, while the most GC-sensitive DP thymocytes died through the activation of mitochondrial apoptotic pathway. Here we analyzed the apoptosis-inducing effect of high dose (10^-6 M) in vitro dexamethasone (DX) treatment in mouse thymic- and splenic Tregs and CD4⁺ T cells. Activation of both extrinsic and intrinsic apoptotic pathways started after 2 h of DX treatment in CD4 SP thymocytes and was 3 × higher than in CD4⁺ splenocytes, while in Treg cells, weak activation of the extrinsic apoptotic pathway started only after 3 h. We also investigated the expression of 21 apoptosis-related molecules using a protein array and found higher level of both pro-and anti-apoptotic molecules in Tregs compared to CD4⁺ T cells. 4 h in vitro DX treatment induced upregulation of most apoptosis-related molecules both in Tregs and CD4⁺ T cells, except for the decrease of Bcl-2 expression in CD4⁺ T cells. We found high basal cytosolic Ca²⁺ levels in untreated Treg cells, which further increased after DX treatment, while the specific TCR-induced Ca²⁺ signal was lower in Tregs than in CD4⁺ T cells. Our results suggest that in the background of the relative apoptosis resistance of Treg cells to GCs might be their high basal cytosolic Ca²⁺ level and upregulated Bcl-2 expression. In contrast, downregulation of Bcl-2 expression in CD4⁺ T cells can explain their higher, DX-induced apoptosis sensitivity.

Prednisolone in early pregnancy inhibits regulatory T cell generation and alters fetal and placental development in mice

Corticosteroids have been utilised in the assisted reproduction setting with the expectation of suppressing aberrant immune activation and improving fertility in women. However, the effects of corticosteroids on fertility, and on pregnancy and offspring outcomes, are unclear. In this study, mice were administered prednisolone (1 mg/kg) or PBS daily in the pre-implantation phase, and effects on the adaptive immune response, the implantation rate, fetal development and postnatal outcomes were investigated. Prednisolone disrupted the expected expansion of CD4+ T cells in early pregnancy, inhibiting generation of both regulatory T cells (Treg cells) and effector T cells and suppressing IFNG required for T cell functional competence. Prednisolone caused an 8-20% increase in the embryo implantation rate and increased the number of viable pups per litter. In late gestation, fetal and placental weights were reduced in a litter size-dependent manner, and the canonical inverse relationship between litter size and fetal weight was lost. The duration of pregnancy was extended by ~ 0.5 day and birth weight was reduced by ~ 5% after prednisolone treatment. Viability of prednisolone-exposed offspring was comparable to controls, but body weight was altered in adulthood, particularly in male offspring. Thus, while prednisolone given in the pre-implantation phase in mice increases maternal receptivity to implantation and resource investment in fetal growth, there is a trade-off in long-term consequences for fetal development, birth weight and offspring health. These effects are associated with, and likely caused by, prednisolone suppression of the adaptive immune response at the outset of pregnancy.

Control of immunity by glucocorticoids in health and disease

Animals receive environmental stimuli from neural signals in order to produce hormones that control immune responses. Glucocorticoids (GCs) are a group of steroid hormones produced in the adrenal cortex and well-known mediators for the nervous and immune systems. GC secretion is induced by circadian rhythm and stress, and plasma GC levels are high at the active phase of animals and under stress condition. Clinically, GCs are used for allergies, autoimmunity, and chronic inflammation, because they have strong anti-inflammatory effects and induce the apoptosis of lymphocytes. Glucocorticoid receptor (GR) acts as a transcription factor and represses the expression of inflammatory cytokines, chemokines, and prostaglandins by binding to its motif, glucocorticoid-response element, or to other transcription factors. In mice, GR suppresses the antigen-stimulated inflammation mediated by macrophages, dendritic cells, and epithelial cells, and impairs cytotoxic immune responses by downregulating interferon-γ production and inhibiting the development of type-1 helper T cells, CD8+ T cells, and natural killer cells. These immune inhibitory effects prevent lethality by excessive inflammation, but at the same time increase the susceptibility to infection and cancer. GCs can also activate the immune system. The circadian cycle of GC secretion controls the diurnal oscillations of the distribution and response of T cells, thus supporting T cell maintenance and effective immune protection against infection. Moreover, several reports have shown that GR has the potential to enhance the activities of Th2, Th17, and immunoglobulin-producing B cells. Stress has two different effects on immune responses: immune suppression to cause mortality by infection and cancer, and excessive immune activation to induce chronic inflammation and autoimmune disease. Consistently, stress-induced GCs strongly suppress cell-mediated immunity and cause viral infection and tumor development. They may also enhance the development of pathogenic helper T cells and cause tissue damage through neural and intestinal inflammation. Past studies have reported the positive and negative effects of GCs on the immune system. These opposing properties of GCs may regulate the immune balance between the responsiveness to antigens and excessive inflammation in steady-state and stress conditions.

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.

Hydroxysafflor Yellow A Alleviates Ovalbumin-Induced Asthma in a Guinea Pig Model by Attenuateing the Expression of Inflammatory Cytokines and Signal Transduction

Hydroxysafflor yellow A (HSYA) is an effective ingredient of the Chinese herb Carthamus tinctorius L. In this study, we aimed to evaluate the effects of HSYA on ovalbumin (OVA)-induced asthma in guinea pigs, and to elucidate the underlying mechanisms. We established a guinea pig asthma model by intraperitoneal injection and atomized administration OVA. Guinea pigs were injected intraperitoneally with HSYA (50, 75, 112.5 mg/kg) once daily from days 2 to 22 before OVA administration. We examined biomarkers including lung function, pulmonary histopathology, immunoglobulin E (IgE), Th1/Th2 relative inflammatory mediators, and related pathways. Pathological changes in lung tissues were detected by hematoxylin and eosin and periodic acid-Schiff staining. Phosphorylation levels of JNK mitogen-activated protein kinase (MAPK), p38 MAPK, ERK MAPK, and inhibitor of nuclear factor κBα (IκBα) were detected by western blot. plasma levels of total IgE, platelet-activating factor (PAF), and interleukin (IL)-3 were detected by enzyme-linked immunosorbent assay (ELISA). Expression levels of tumor necrosis factor (TNF)-α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-13, and interferon (IFN)-γ were detected by ELISA and real-time quantitative polymerase chain reaction. HSYA significantly reduced airway resistance, improved dynamic lung compliance, and attenuated the pathologic changes. HSYA also inhibited the phosphorylation of JNK MAPK, p38 MAPK, ERK MAPK, and IκBα, and inhibited the OVA-induced elevations of IgE, PAF, IL-1β, IL-6, IL-4, IL-5, and IL-13 and the decreases in TNF-α, IFN-γ, IL-2, and IL-3. These findings suggest that HSYA has a protective effect on OVA-induced asthma through inhibiting the Th1/Th2 cell imbalance and inhibiting activation of the MAPK signaling pathway.

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.

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.

Contrasting impact of corticosteroids on anti-PD-1 immunotherapy efficacy for tumor histologies located within or outside the central nervous system

Immune checkpoint blockade targeting programmed cell death protein 1 (PD-1) is emerging as an important treatment strategy in a growing list of cancers, yet its clinical benefits are limited to a subset of patients. Further investigation of tumor-intrinsic predictors of response and how extrinsic factors, such as iatrogenic immunosuppression caused by conventional therapies, impact the efficacy of anti-PD-1 therapy are paramount. Given the widespread use of corticosteroids in cancer management and their immunosuppressive nature, this study sought to determine how corticosteroids influence anti-PD-1 responses and whether their effects were dependent on tumor location within the periphery versus central nervous system (CNS), which may have a more limiting immune environment. In well-established anti-PD-1-responsive murine tumor models, corticosteroid therapy resulted in systemic immune effects, including severe and persistent reductions in peripheral CD4+ and CD8 + T cells. Corticosteroid treatment was found to diminish the efficacy of anti-PD-1 therapy in mice bearing peripheral tumors with responses correlating with peripheral CD8/Treg ratio changes. In contrast, in mice bearing intracranial tumors, corticosteroids did not abrogate the benefits conferred by anti-PD-1 therapy. Despite systemic immune changes, anti-PD-1-mediated antitumor immune responses remained intact during corticosteroid treatment in mice bearing intracranial tumors. These findings suggest that anti-PD-1 responses may be differentially impacted by concomitant corticosteroid use depending on tumor location within or outside the CNS. As an immune-specialized site, the CNS may potentially play a protective role against the immunosuppressive effects of corticosteroids, thus sustaining antitumor immune responses mediated by PD-1 blockade.

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.

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.

Glucocorticoid hormone treatment enhances the cytokine production of regulatory T cells by upregulation of Foxp3 expression

OBJECTIVE

Despite the fact that glucocorticoids (GC) are important therapeutic tools, their effects on regulatory T cells (Treg) are not well defined. The aim of our work was to investigate how GCs influence in vivo the thymic (tTreg) and peripheral Treg (pTreg) differentiation, survival and cytokine production.

METHODS

Tregs were detected with flow cytometry in lymphatic organs of 4-6 weeks old BALB/c mice after repeated (2-4days), high-dose in vivo GC treatment using CD4/CD25 cell surface and Foxp3/IL-10/TGFβ/glucocorticoid receptor (GR) intracellular staining. Cytokine, Foxp3, and GR mRNA levels of sorted CD4⁺CD25^high T cells were analyzed using RT-PCR. Foxp3 and GR localization in Treg cells was investigated with confocal microscopy.

RESULTS

GC treatment of mice resulted in increased relative tTreg frequency in the thymus, which was due to decreased total thymocyte numbers with unchanged absolute tTreg cell count. In contrast the relative pTreg cell ratio in secondary lymphatic organs decreased or showed no changes after GC treatment, while the absolute number of pTregs decreased. Elevated intracellular IL-10⁺ and TGFβ⁺ tTreg and pTreg ratios were measured in GC-treated animals, accompanied with elevated Foxp3 mRNA expression. In addition, GC treatment caused increased TGFβ and IL-35 mRNA expression in CD4⁺CD25^high+ splenic and elevated IL-10 mRNA level in thymic tTregs. GR expression of thymic tTreg cells was lower than in pTregs. GC treatment caused an opposite change in GR levels, elevating GR in tTregs but decreasing it in pTregs. We observed a nuclear localization of GR in both tTregs and pTregs, which showed high colocalization (∼60%) with Foxp3 transcription factor. These data suggest an interaction of these two transcription factors with further increase due to GC treatment in splenic pTregs.

CONCLUSION

Our data show selective survival of tTregs and elevated production of immunosuppressive cytokines by Treg cells after GC treatment, which may contribute to the immunosuppressive effects of GCs.

Neuropsychiatry phenotype in asthma: Psychological stress-induced alterations of the neuroendocrine-immune system in allergic airway inflammation

Since the recognition of asthma as a syndrome with complex pathophysiological signs and symptoms, recent research has sought to classify asthma phenotypes based on its clinical and molecular pathological features. Psychological stress was first recognized as a potential immune system modulator of asthma at the end of the 19th century. The activation of the central nervous system (CNS) upon exposure to psychological stress is integral for the initiation of signal transduction processes. The stress hormones, including glucocorticoids, epinephrine, and norepinephrine, which are secreted following CNS activation, are involved in the immunological alterations involved in psychological stress-induced asthma exacerbation. The mechanisms underlying this process may involve a pathological series of events from the brain to the lungs, which is attracting attention as a conceptually advanced phenotype in asthma pathogenesis. This review presents insights into the critical role of psychological stress in the development and exacerbation of allergic asthma, with a special focus on our own data that emphasizes on the continuity from the central sensing of psychological stress to enhanced eosinophilic airway inflammation.

Bystander immunotherapy as a strategy to control allergen-driven airway inflammation

Allergic asthma is a chronic inflammatory disease characterized by airway hyperresponsiveness (AHR), lung infiltration of Th2 cells, and high levels of IgE. To date, allergen-specific immunotherapy (SIT) is the only treatment that effectively alleviates clinical symptoms and has a long-term effect after termination. Unfortunately, SIT is unsuitable for plurisensitized patients, and highly immunogenic allergens cannot be used. To overcome these hurdles, we sought to induce regulatory CD4(+) T cells (Treg) specific to an exogenous antigen that could be later activated as needed in vivo to control allergic responses. We have established an experimental approach in which mice tolerized to ovalbumin (OVA) were sensitized to the Leishmania homolog of receptors for activated c kinase (LACK) antigen, and subsequently challenged with aerosols of LACK alone or LACK and OVA together. Upon OVA administration, AHR and allergic airway responses were strongly reduced. OVA-induced suppression was mediated by CD25(+) Treg, required CTLA-4 and ICOS signaling and resulted in decreased numbers of migrating airway dendritic cells leading to a strong impairment in the proliferation of allergen-specific Th2 cells. Therefore, inducing Treg specific to a therapeutic antigen that could be further activated in vivo may represent a safe and novel curative approach for allergic asthma.

Dexamethasone suppresses allergic rhinitis and amplifies CD4(+) Foxp3(+) regulatory T cells in vitro

BACKGROUND

Glucocorticosteroids (GCs) are highly effective in mitigating allergic inflammation. In this study, we investigate the effects of dexamethasone (DEX) on regulatory T cells (Tregs) in a murine model of allergic rhinitis (AR).

METHODS

BALB/c mice were sensitized to ovalbumin (OVA) followed by intranasal OVA challenge. Mice in the treatment group received DEX by intraperitoneal injection (5 mg/kg/day) 1 hour before the OVA challenge. Further, CD4(+) CD25(-) T cells from the spleens were cultured in presence of DEX. The effects of DEX on CD4(+) Foxp3(+) T cells were then assessed in vivo as well as in vitro.

RESULTS

Frequencies of sneezing and scratching decreased significantly in the DEX-treated group compared to that in the OVA group. Histopathological analyses showed that DEX restored the destroyed and discontinuous ciliated epithelium of the nasal mucosa in the OVA group. Moreover, DEX inhibited the production of interleukin (IL)-4, IL-5, and IL-13 in the nasal cavity lavage fluid in this group. We also observed a significant increase in the percentage of CD4(+) Foxp3(+) T cells in the OVA group. In vivo, DEX treatment significantly decreased the number of CD4(+) Foxp3(+) T cells. However, in vitro, the proportion of these cells increased in the presence of DEX. Furthermore, the number of late stage apoptotic CD4(+) T cells was also significantly increased upon exposure to DEX.

CONCLUSION

DEX therapy effectively suppresses AR symptoms, but does not result in the expected increase in the frequency of Tregs in vivo. Thus, whether GCs exert immunosuppressive effects by influencing the number of Tregs remains unresolved.

Glucocorticoids decrease Treg cell numbers in lungs of allergic mice

Glucocorticoids have been the hallmark anti-inflammatory drug used to treat asthma. It has been shown that glucocorticoids ameliorate asthma by increasing numbers and activity of Tregs, in contrast recent data show that glucocorticoid might have an opposite effect on Treg cells from normal mice. Since Tregs are target cells that act on the resolution of asthma, the aim of this study was to elucidate the effect of glucocorticoid treatment on lung Tregs in mouse models of asthma. Allergen challenged mice were treated with either oral dexamethasone or nebulized budesonide. Broncoalveolar lavage and airway hyperresponsiveness were evaluated after allergenic challenge. Lung, thymic and lymph node cells were phenotyped on Treg through flow cytometry. Lung cytokine secretion was detected by ELISA. Although dexamethasone inhibited airway inflammation and hyperresponsiveness, improving resolution, we have found that both dexamethasone and budesonide induce a reduction of Treg numbers on lungs and lymphoid organs of allergen challenged mice. The reduction of lung Treg levels was independent of mice strain or type of allergen challenge. Our study also indicates that both glucocorticoids do not increase Treg activity through production of IL-10. Glucocorticoid systemic or localized treatment induced thymic atrophy. Taken together, our results demonstrate that glucocorticoids decrease Treg numbers and activity in different asthma mouse models, probably by reducing thymic production of T cells. Therefore, it is possible that glucocorticoids do not have beneficial effects on lung populations of Treg cells from asthmatic patients.

The involvement of glucocorticoids in psychological stress-induced exacerbations of experimental allergic asthma

BACKGROUND

Psychological stress is associated with the aggravation of asthma symptoms. Glucocorticoids (GC), which are stress hormones released upon exposure to stress, have the potential to shift immune responses towards a predominant Th2 response by priming antigen-presenting cells to produce lower levels of IL-12 as well as reducing the development of regulatory T cells. However, the involvement of GC in psychological stress-induced exacerbations of allergic asthma has not yet been clarified.

METHODS

Sensitized mice were exposed to restraint stress followed by forced swimming stress, during which a GC receptor antagonist or a GC synthesis inhibitor was administered, and then antigen was inhaled. Corticosterone levels in the blood were measured in stressed and nonstressed mice. After antigen inhalation, the airway responses to aerosolized methacholine, epithelial mucus secretion and airway inflammation were evaluated, and the IL-13 contents in bronchoalveolar lavage fluid were measured.

RESULTS

The exposure to stress significantly increased corticosterone levels. Allergic airway responses and the increase of IL-13 contents evoked by antigen inhalation were significantly higher in stressed mice than in nonstressed mice. The administration of a GC receptor antagonist and a GC synthesis inhibitor during stress exposure significantly reduced the exacerbation of the airway responses and the increase of IL-13 contents in stressed mice challenged with antigen.

CONCLUSIONS

These results indicate that the increased release of GC upon exposure to stress has a priming effect on the aggravation of allergic airway responses following the exposure, suggesting a pathophysiological role for the neuroendocrine axis in linking psychological stress to asthma exacerbations.

Effect of prednisone on nasal symptoms and peripheral blood T-cell function in chronic rhinosinusitis

BACKGROUND

Systemic corticosteroids are the most effective anti-inflammatory drugs used for controlling chronic rhinosinusitis (CRS) symptoms. The potential mechanisms for their beneficial effects include increasing the number and function of T regulatory cells (Tregs), as reported in the local tissue post-intranasal steroid treatment. We investigated the effect of systemic corticosteroids on peripheral blood (PB) Tregs in subjects with CRS.

METHODS

Twenty CRS subjects and 19 controls were recruited. PB mononuclear cells (PBMCs) were isolated from CRS subjects before and after systemic corticosteroid administration in the course of clinical treatment. Control subjects received no treatment and were studied at one visit. Nasal symptoms were recorded. CD4(+) CD25(+) Foxp3(+) cells (Tregs) were analyzed by flow cytometry. Messenger RNA (mRNA) levels for interferon γ (IFN-γ), interleukin 4 (IL-4), IL-10, IL-13, IL-17A, transforming growth factor β1 (TGF-β1), forkhead box P3 (FoxP3), and GATA-binding factor 3 (GATA-3) were measured in PBMCs using real-time polymerase chain reaction (PCR).

RESULTS

CRS subjects reported improved nasal symptoms (p = 0.005) and significantly reduced PB Tregs after treatment with corticosteroids (p = 0.042). The transcript levels of IL-4 and GATA-3 were significantly higher in the CRS subjects at their first visit when compared to controls (p = 0.019 and p = 0.05, respectively). Corticosteroid treatment lowered the transcript levels of immunoregulatory transcription factors [FoxP3 (p = 0.048) and GATA-3 (p = 0.012)] and IFN-γ (p = 0.036) in PB.

CONCLUSION

In contrast to prior work in local nasal tissue, our study reports reduced PB Tregs and decreased T helper 1 (T(H)1) and T(H)2 function after treatment with systemic corticosteroids. These data indicate that corticosteroid effects on Tregs in CRS are complex involving local signals in the tissue that are distinct from those in circulating cells.

Essential roles of endogenous glucocorticoids and TNF/TNFR1 in promoting bone-marrow eosinopoiesis in ovalbumin-sensitized, airway-challenged mice

AIMS

Stress mechanisms paradoxically contribute to allergic episodes in humans and mice. Glucocorticoids (GC) and interleukin (IL)-5 synergically upregulate murine bone-marrow eosinophil production. Here we explored the role of endogenous GC in allergen-stimulated bone-marrow eosinophil production in ovalbumin-sensitized/challenged mice.

MAIN METHODS

In BALB/c or C57BL/6 mice, sensitized and intranasally challenged with ovalbumin, we monitored eosinophil numbers in freshly harvested or cultured bone-marrow, and plasma corticosterone levels. Metyrapone (MET) was used to inhibit GC synthesis, and RU486 to block GC actions. In sensitized mice challenged intraperitoneally, we examined the relationship between eosinophilia of bone-marrow and peritoneal cavity, in the absence or presence of RU486. In experiments involving in vivo neutralization of tumor necrosis factor-α (TNF) by specific antibodies, or using mice which lack functional type I TNF receptors (TNFRI), we evaluated the relationship between TNF blockade, corticosterone levels, RU486 or MET treatment and challenge-induced bone-marrow eosinophilia.

KEY FINDINGS

RU486 or MET pretreatments abolished challenge-induced increases in eosinophil numbers in bone-marrow (in vivo and ex vivo), and in the peritoneal cavity. MET, but not RU486, prevented the challenge-induced increase in corticosterone levels. Challenge-induced bone-marrow eosinophilia and corticosterone surge were abolished in TNFRI-deficient mice. Anti-TNF-treatment very effectively prevented challenge-induced bone-marrow eosinophilia, in the absence of RU486 or MET, but had no independent effect in the presence of either drug.

SIGNIFICANCE

Endogenous GC was essential for allergen challenge-induced increases in eosinophil numbers inside bone-marrow. This effect required TNF and TNFRI, which suggests an immunoendocrine mechanism.

Regulatory and effector T-cells are differentially modulated by Dexamethasone

It is assumed that the ratio between effector T cells (Teff) and regulatory T cells (Tregs) controls the immune reactivity within the T-cell compartment. The purpose of this study was to investigate if Dexamethasone (Dex) affects Teff and Tregs subsets. Dex induced on Tregs a dose and time-dependent apoptosis which resulted in a relative increase of Teff. After TCR activation, Dex induced a strong proliferative inhibition of Teff, but a weaker proliferative inhibition on Tregs. These effects were modulated by IL-2, which not only restored the proliferative response, but also prevented Dex-induced apoptosis. The highest dose of IL-2 prevented apoptosis on all FOXP3+CD4+ T cells. Meanwhile, the lowest dose only rescued activated Tregs (aTregs), probably related to their CD25 higher expression. Because Dex did not affect the suppressor capacity of aTregs either, our results support the notion that under Dex treatment, the regulatory T-cell compartment maintains its homeostasis.

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.

Effects of systemic versus local administration of corticosteroids on mucosal tolerance

Respiratory exposure to allergen induces T cell tolerance and protection against the development of airway hyperactivity in animal models of asthma. Whereas systemic administration of dexamethasone during the delivery of respiratory Ag has been suggested to prevent the development of mucosal tolerance, the effects of local administration of corticosteroids, first-line treatment for patients with bronchial asthma, on mucosal tolerance remain unknown. To analyze the effects of systemic versus local administration of different types of corticosteroids on the development of mucosal tolerance, mice were exposed to respiratory allergen to induce mucosal tolerance with or without systemic or intranasal application of different doses of dexamethasone or prednisolone. After the induction of mucosal tolerance, proliferation of T cells was inhibited in tolerized mice, whereas systemic applications of corticosteroids restored T cell proliferation and secretion of Th2 cytokines. In contrast, inhaled corticosteroids showed no effect on both T cell proliferation and cytokine secretion. In addition, mice systemically treated with corticosteroids showed an increased airway hyperactivity with a significant lung inflammation, but also an increased T effector cells/regulatory T cells ratio in the second lymphoid organs when compared with mice that receive corticosteroids by inhalation. These results demonstrate that local administration of corticosteroids has no effect on the development of immune tolerance in contrast to systemically applied corticosteroids. Furthermore, although different concentrations of corticosteroids are administered to patients, our results demonstrated that the route of administration rather than the doses affects the effect of corticosteroids on respiratory tolerance induction. Considering the broad application of corticosteroids in patients with allergic disease and asthma, the route of administration of steroid substances seems crucial in terms of treatment and potential side effects. These findings may help elucidate the apparently contradicting results of corticosteroid treatment in allergic diseases.

The impact of oral versus inhaled glucocorticoids on allergen specific IgE testing in experimentally asthmatic cats

Glucocorticoids (GCs) are palliative for allergic asthma, but allergen-specific immunotherapy (ASIT), which relies on identification of allergens, represents a potentially curative treatment. The purpose of this study was to determine if oral or inhaled GCs would interfere with identification of sensitizing allergens. The hypothesis was that oral but not inhaled GCs would interfere with accurate allergen-specific IgE identification determined by skin and serum testing in experimentally asthmatic cats. Asthma was induced in 18 cats using Bermuda grass allergen (BGA). Cats (n=6/group) were randomized to receive oral GCs (10mg prednisolone q 24 h), inhaled GCs (600 μg budesonide q 24 h) or placebo (q 24 h PO) for one month. Intradermal skin testing (IDST) and serum BGA-specific IgE were measured prior to, during and after treatment. A paired t test was used to compare groups pre- and post-treatment (P<0.05 significant). IDST reactivity was eliminated in 4/6, 3/6, and 1/6 cats receiving oral GCs, inhaled GCs, and placebo respectively. Two weeks after stopping treatment, IDST was again positive in all cats. Serum IgE reactivity to BGA was not significantly diminished by any treatment. In conclusion, a two-week withdrawal from GCs is adequate for IDST, but may not be necessary for serum IgE testing.

Influence of short-term glucocorticoid therapy on regulatory T cells in vivo

BACKGROUND

Pre- and early clinical studies on patients with autoimmune diseases suggested that induction of regulatory T(T(reg)) cells may contribute to the immunosuppressive effects of glucocorticoids (GCs).

OBJECTIVE

We readdressed the influence of GC therapy on T(reg) cells in immunocompetent human subjects and naïve mice.

METHODS

Mice were treated with increasing doses of intravenous dexamethasone followed by oral taper, and T(reg) cells in spleen and blood were analyzed by FACS. Sixteen patients with sudden hearing loss but without an inflammatory disease received high-dose intravenous prednisolone followed by stepwise dose reduction to low oral prednisolone. Peripheral blood T(reg) cells were analyzed prior and after a 14 day GC therapy based on different markers.

RESULTS

Repeated GC administration to mice for three days dose-dependently decreased the absolute numbers of T(reg) cells in blood (100 mg dexamethasone/kg body weight: 2.8±1.8×10(4) cells/ml vs. 33±11×10(4) in control mice) and spleen (dexamethasone: 2.8±1.9×10(5)/spleen vs. 95±22×10(5)/spleen in control mice), which slowly recovered after 14 days taper in spleen but not in blood. The relative frequency of FOXP3(+) T(reg) cells amongst the CD4(+) T cells also decreased in a dose dependent manner with the effect being more pronounced in blood than in spleen. The suppressive capacity of T(reg) cells was unaltered by GC treatment in vitro. In immunocompetent humans, GCs induced mild T cell lymphocytosis. However, it did not change the relative frequency of circulating T(reg) cells in a relevant manner, although there was some variation depending on the definition of the T(reg) cells (FOXP3(+): 4.0±1.5% vs 3.4±1.5%*; AITR(+): 0.6±0.4 vs 0.5±0.3%, CD127(low): 4.0±1.3 vs 5.0±3.0%* and CTLA4+: 13.8±11.5 vs 15.6±12.5%; * p<0.05).

CONCLUSION

Short-term GC therapy does not induce the hitherto supposed increase in circulating T(reg) cell frequency, neither in immunocompetent humans nor in mice. Thus, it is questionable that the clinical efficacy of GCs is achieved by modulating T(reg) cell numbers.

Effects of formoterol-budesonide on airway remodeling in patients with moderate asthma

AIM

To evaluate the effect of inhaled formoterol-budesonide on airway remodeling in adult patients with moderate asthma.

METHODS

Thirty asthmatic patients and thirty control subjects were enrolled. Asthmatic subjects used inhaled Symbicort 4.5/160 μg twice daily for one year. The effect of formoterol-budesonide on airway remodeling was assessed with comparing high-resolution computer tomography (HRCT) images of asthmatic patients and controls, as well as expression levels of cytokines and growth factors, inflammatory cell count in induced sputum, and airway hyper-responsiveness.

RESULTS

The differences in age and gender between the two groups were not significant. However, differences in FVC %pred, FEV(1) %pred, and PC(20) between the two groups were significant. After treatment with formoterol-budesonide, the asthma patients' symptoms were relieved, and their lung function was improved. The WT and WA% of HRCT images in patients with asthma was increased, whereas treatment with formoterol-budesonide caused these values to decrease. The expression of MMP-9, TIMP-1, and TGF-β(1) in induced sputum samples increased in patients with asthma and decreased dramatically after treatment with formoterol-budesonide. The WT and WA% are correlated with the expression levels of cytokines and growth factors, inflammatory cell count in induced sputum, and airway hyper-responsiveness, while these same values are correlated negatively with FEV(1)/FVC and FEV(1)%.

CONCLUSION

Formoterol-budesonide might interfere in chronic inflammation and airway remodeling in asthmatic patients. HRCT can be used to effectively evaluate airway remodeling in asthmatic patients.

Induction of tolerogenic lung CD4+ T cells by local treatment with a pSTAT-3 and pSTAT-5 inhibitor ameliorated experimental allergic asthma

Signal transducer and activator of transcription (STAT)-3 inhibitors play an important role in regulating immune responses. Galiellalactone (GL) is a fungal secondary metabolite known to interfere with the binding of phosphorylated signal transducer and activator of transcription (pSTAT)-3 as well of pSTAT-6 dimers to their target DNA in vitro. Intra nasal delivery of 50 μg GL into the lung of naive Balb/c mice induced FoxP3 expression locally and IL-10 production and IL-12p40 in RNA expression in the airways in vivo. In a murine model of allergic asthma, GL significantly suppressed the cardinal features of asthma, such as airway hyperresponsiveness, eosinophilia and mucus production, after sensitization and subsequent challenge with ovalbumin (OVA). These changes resulted in induction of IL-12p70 and IL-10 production by lung CD11c(+) dendritic cells (DCs) accompanied by an increase of IL-3 receptor α chain and indoleamine-2,3-dioxygenase expression in these cells. Furthermore, GL inhibited IL-4 production in T-bet-deficient CD4(+) T cells and down-regulated the suppressor of cytokine signaling-3 (SOCS-3), also in the absence of STAT-3 in T cells, in the lung in a murine model of asthma. In addition, we found reduced amounts of pSTAT-5 in the lung of GL-treated mice that correlated with decreased release of IL-2 by lung OVA-specific CD4(+) T cells after treatment with GL in vitro also in the absence of T-bet. Thus, GL treatment in vivo and in vitro emerges as a novel therapeutic approach for allergic asthma by modulating lung DC phenotype and function resulting in a protective response via CD4(+)FoxP3(+) regulatory T cells locally.

Regulatory T cells in many flavors control asthma

That regulatory T cells (Tregs) have a crucial role in controlling allergic diseases such as asthma is now undisputed. The cytokines most commonly implicated in Treg-mediated suppression of allergic asthma are transforming growth factor-beta (TGF-beta) and interleukin (IL)-10). In addition to naturally occurring Tregs, adaptive Tregs, induced in response to foreign antigens, have been shown in recent studies. The concept of inducible/adaptive Tregs (iTregs) has considerable significance in preventing asthma if generated early enough in life. This is because cytokines such as IL-4 and IL-6 inhibit Foxp3 induction in naive CD4+ T cells and therefore de novo generation of Tregs can be expected to be less efficient when it is concomitant with effector cell development in response to an allergen. However, if iTregs can be induced, the process of infectious tolerance would facilitate expansion of the iTreg pool as suggested in the recent literature. It is tempting to speculate that there is a window of opportunity in early life in the context of a relatively immature immune system that is permissive for the generation of iTregs specific to a spectrum of allergens that would regulate asthma for lifelong. The focus of this review is the relevance of nTregs and iTregs in controlling asthma from early life into adulthood, the mechanisms underlying Treg function, and the prospects for using our current concepts to harness the full potential of Tregs to limit disease development and progression.

Pneumococcal vaccines for allergic airways diseases

BACKGROUND

Asthma is a common global health problem. Environmental exposures such as bacteria may protect against asthma development.

OBJECTIVE

This review aims to examine the possible protective role of pneumococcal infection and vaccination in asthma.

METHODS

A review of known experimental biology and human epidemiology relating to asthma and pneumococcal infection was performed.

RESULTS

Pneumococcal infection can modulate components of allergic airways disease such as airways hyperresponsiveness and airway eosinophilia. Exposure to killed pneumococcus can reproduce these effects and the mechanism may involve control by T regulatory cells.

CONCLUSIONS

Pneumococcal immunoregulatory therapy is a potentially important approach to asthma management that requires further evaluation in well-designed research studies.

Harnessing regulatory T cells to suppress asthma: from potential to therapy

Regulatory T cells (Tregs) play an essential role in maintaining the homeostatic balance of immune responses. Asthma is an inflammatory condition of the airways that is driven by dysregulated immune responses toward normally innocuous antigens. Individuals with asthma have fewer and less functional Tregs, which may lead to uncontrolled effector cell responses and promote proasthmatic responses of T helper type 2, T helper 17, natural killer T, antigen-presenting, and B cells. Tregs have the capacity to either directly or indirectly suppress these responses. Hence, the induced expansion of functional Tregs in predisposed or individuals with asthma is a potential approach for the prevention and treatment of asthma. Infection by a number of micro-organisms has been associated with reduced prevalence of asthma, and many infectious agents have been shown to induce Tregs and reduce allergic airways disease in mouse models. The translation of the regulatory and therapeutic properties of infectious agents for use in asthma requires the identification of key modulatory components and the development and trial of effective immunoregulatory therapies. Further translational and clinical research is required for the induction of Tregs to be harnessed as a therapeutic strategy for asthma.

The effect of oral steroids with and without vitamin D3 on early efficacy of immunotherapy in asthmatic children

BACKGROUND

The possibility of additional strategies to enhance the effectiveness of specific immunotherapy (SIT) is highly attractive.

AIM

The aim of our study was to assess the influence of oral corticosteroids and oral corticosteroids combined with vitamin D(3) on the early clinical and immunological effects of SIT.

METHODS

It was a randomized, double-blind, placebo-controlled trial conducted in 54 asthmatic children allergic to house dust mites. Intervention was based on receiving a single dose of oral steroid, with or without vitamin D(3), or placebo only on the day of the build-up phase of SIT.

RESULTS

After 12 months of SIT, the median daily inhaled corticosteroid (ICS) dose, which controls the symptoms of asthma, was reduced by 25% in the steroid group. However, a 50% reduction of the median daily ICS dose was observed in the control group. The clinical effects of SIT were not affected in the steroid+D(3) group. Concomitantly, we found that intervention with prednisone significantly impaired the induction of T regulatory lymphocytes. Importantly, the clinical and immunological effects of SIT were not affected by intervention with steroids administered with vitamin D(3).

CONCLUSIONS

Our study failed to show a beneficial effect of oral corticosteroids on allergen-specific immunotherapy. We observed that the combined administration of a corticosteroid drug and allergen extract suppressed the early clinical and immunological effects of SIT and that vitamin D(3) prevented this 'adverse' influence of steroids.

Steroid treatments in mice do not alter the number and function of regulatory T cells, but amplify cyclophosphamide-induced autoimmune disease

Corticosteroids are commonly used in the therapy of autoimmune disease (AID), although they are rarely, if ever, curative. This failure may result from their deleterious effects on regulatory T cells (Treg). In this work, we directly tested the effects of hydrocortisone (HC) administration on Treg number and function in established mouse models of multiple sclerosis and colitis. Treatment with pertussis toxin (Ptx) or Cyclophosphamide (Cyp), two compounds known to affect Treg function served as controls. We first show that contrarily to Ptx, HC administration to mice transgenic for a TCR specific to myelin basic protein induces a mild lymphopenia, without selective depletion of Treg, nor induction of experimental autoimmune encephalomyelitis (EAE). We next report that HC administration to normal mice has no effect on Treg suppressive function tested in vitro. Moreover, we document that Treg isolated from HC-treated animals maintain their capacity to prevent T cell-induced colitis. In contrast, the combined administration of HC and Cyp, as is frequently used in the therapy of severe AID, dramatically enhanced the deleterious effect of Cyp on Treg number and function. Our analysis indicates that while a short course of corticosteroids alone is not deleterious to immune regulation, combined therapies, notably with Cyp, should be avoided.

Quantification and molecular characterization of regulatory T cells in connective tissue diseases

The aim of our study was to investigate and characterize regulatory T cells (Treg) in peripheral blood of patients with connective tissue diseases (Systemic lupus erythematosus, systemic sclerosis, Sjögren's syndrome, poly- and dermatomyositis) as compared with blood from healthy controls. Treg cells were quantified and phenotypically characterized by flow cytometry while the expression level of Foxp3 mRNA was evaluated by real time PCR. A reduced percentage of peripheral blood Treg cells was found in patients than in controls, irrespective of the type of connective tissue disease. Treg cells, especially those expressing one of the phenotypical markers, seemed to differ not only between patients and healthy controls but also among types of diseases. Additionally, the presence of autoantibodies as well as disease activity appeared to be correlated with particular Treg cell populations, especially those expressing one of the examined phenotypical markers. Correlations with therapy suggested that glucocorticoids plus antimalarial or other immunosuppressor drugs diminished the percentage of Treg cells, especially of those with memory phenotype. These findings indicated dysregulations at the level of Treg cells and suggested an involvement of these cells in the pathology of connective tissue diseases. Moreover, our data are in agreement with the suggestion that Treg cells could be therapeutic targets for some autoimmune diseases.

Handbook of experimental pharmacology "dendritic cells": the use of dexamethasone in the induction of tolerogenic DCs

Dendritic cells (DCs) have a central role in immune regulation, ranging from tolerance induction to the induction of specific immune responses. DCs serve as an essential link between innate and adaptive immunity. This broad range of powerful immune stimulatory as well as regulatory functions has made DCs as targets for vaccine development strategies. One approach to promote the tolerogenicity of DCs is to suppress their maturation by pharmacological agents, including glucocorticoids (GCs). In the present chapter we will review GCs used in vitro with cultured DCs, applied in vivo, or used to generate tolerogenic DCs for cellular therapy.

The effects of immunosuppression on regulatory CD4(+)CD25(+) T cells: impact on immunosuppression selection in transplantation

During immune response and T-cell activation, both effector T cells and regulatory T(T(reg)) cells are activated and regulated simultaneously by both positive and negative pathways. CD4(+)CD25(+) T(reg) cells play a critical role in immune tolerance to self antigens as well as to allografts in some transplant settings. Effective immunosuppressive regimens significantly reduced the incidence of acute allograft rejection in patients following organ transplantation. However, the impact of immunosuppressive treatment on the potential induction of transplant tolerance has not been well determined. In this review we summarize the effects of immunosuppressive reagents on CD4(+)CD25(+) T(reg) cells in order to bring attention to this issue, which may affect the choice of immunosuppressive regimen in the clinical setting.

The role of anti-IgE therapy in combination with allergen specific immunotherapy for seasonal allergic rhinitis

Novel therapies that interfere specifically with immunologic mechanisms underlying allergen-induced pathology are currently in clinical evaluation. Among these is anti-IgE, which directly targets IgE serum antibodies, thus inhibiting the central mechanism of immediate-type hypersensitivity reactions. Application of anti-IgE antibodies effectively reduces IgE serum levels regardless of allergen specificity. Anti-IgE therapy has been successfully tested in patients with allergic rhinitis, asthma, and food allergy, showing significant efficacy in reducing symptom scores and the use of rescue medications. However, such therapy is limited by high costs and the requirements for permanent or every-season treatment. The advantage of specific immunotherapy (SIT) is the potential to alter the course of the disease, which has been demonstrated in patients with allergic rhinitis, insect venom allergy and, to a lesser degree, asthma. The broader application of SIT is restricted by sometimes life-threatening adverse effects. The combination of anti-IgE with SIT was suggested to be superior to each single treatment protocol in children and adolescents with allergic rhinitis. In a randomized, double-blind trial to assess the efficacy and safety of anti-IgE (omalizumab) or placebo in combination with SIT (birch pollen or grass pollen), the combination therapy reduced symptom load, the sum of daily symptom severity score plus rescue medication use, over the birch and grass pollen seasons by nearly 50% over SIT alone. These data show that the combination of anti-IgE plus SIT may be beneficial for the treatment of allergic diseases, offering improved efficacy, limited adverse effects, and potential immune-modifying effects.

Adjuvanted rush immunotherapy using CpG oligodeoxynucleotides in experimental feline allergic asthma

Allergic asthma is driven by relative overexpression of Th2 cell-derived cytokines in response to aeroallergens. In independent studies, both allergen-specific rush immunotherapy (RIT) and CpG oligodeoxynucleotides (ODN) showed promise in blunting eosinophilic inflammation in a model of feline allergic asthma. We hypothesized that RIT using allergen and CpG ODN would work synergistically to dampen the asthmatic phenotype in experimentally asthmatic cats. Twelve cats with asthma induced using Bermuda grass allergen (BGA) were studied. Of these, six were administered adjuvanted BGA RIT using CpG ODN #2142; six were administered placebo (saline) RIT and later crossed over to adjuvanted RIT. Over 2 days, subcutaneous CpG ODN (0.5ng/kg) with BGA (increasing doses every 2h from 20 to 200microg) was administered. Adverse events were recorded and compared with historical controls. Percentage of eosinophils in bronchoalveolar lavage fluid (BALF), % peripheral CD4+CD25+ T regulatory cells (Tregs), lymphocyte proliferation in response to ConA, and cytokine concentrations in BALF were measured over 2 months. Group mean BALF % eosinophils for the adjuvanted RIT cats were significantly lower at week 1 and month 1 (p=0.03 for both), and marginally significantly lower at month 2 (p=0.09) compared with placebo RIT cats. By the end of the study, 8/12 treated cats had BALF % eosinophils within the reference range for healthy cats. Adjuvanted RIT, but not placebo RIT, cats had significant decreases in the ConA stimulation index over time (p=0.05). BALF IL-4 concentrations were significantly higher at week 1 in adjuvanted RIT cats compared with baseline and month 2, and also with placebo RIT cats at week 1. No significant differences were detected between treatments or over time for IL-10 or IFN-gamma concentrations in BALF or for %Tregs cells in peripheral blood. Adjuvanted RIT using CpG ODN in experimental feline asthma dampens eosinophilic airway inflammation. Adverse effects associated with adjuvanted RIT were less severe compared with a historical, non-adjuvanted RIT protocol. The exact mechanism(s) by which adjuvanted RIT alters the aberrant allergic immune response were not elucidated in this study.

A negative regulatory role in mouse cardiac transplantation for a splice variant of CD80

BACKGROUND

Members of the B7 costimulatory protein family (CD80 and CD86) play a determining role in allograft rejection. Both CD80 and CD86 have naturally occurring splice variants whose roles in transplantation are unknown. Full length CD80 has two immunoglobulin (Ig)-like domains in the extracellular portion, IgC and IgV. In mouse, the isoform IgV-CD80 lacks the IgC-like domain. Here we analyzed the role of mouse IgV-CD80 in heart allograft rejection and search for equivalent splice variants in human.

METHODS

Mice made deficient for full-length CD80 but which retain expression of the shorter IgV-CD80 (CD80 mice) were used as donor or recipient of a heart allograft. Recipient animals were untreated or pretreated with alloantigen expressing cells and/or treated with CD80 and CTLA4 monoclonal antibodies (mAbs).

RESULTS

Recipients expressing IgV-CD80 but not full length CD80 exhibited a slight prolongation in survival of either wild-type (Wt) or CD80 grafts. More dramatically, CD80 animals pretreated with donor alloantigen exhibited permanent graft survival, whereas their Wt counterparts rejected their grafts with a median survival of 24 days. This prolonged survival was due to the expression of IgV-CD80 in recipients since treatment with CD80 mAb abrogated the beneficial effect observed. We identified and report here a similar isoform of CD80 from human cDNA encoding a putative soluble, IgV-containing protein.

CONCLUSIONS

IgV-CD80 bearing recipients show enhanced allograft survival especially after donor alloantigen pretreatment. This together with data from other species suggests that regulation delivered by splice variants of CD80 significantly modulates immunity and may be common across the species.

Stem cell factor-mediated activation pathways promote murine eosinophil CCL6 production and survival

Eosinophil activation during allergic diseases has a detrimental role in the generation of pathophysiologic responses. Stem cell factor (SCF) has recently shown an inflammatory, gene-activating role on eosinophils and contributes to the generation of pathophysiologic changes in the airways during allergic responses. The data in the present study outline the signal transduction events that are induced by SCF in eosinophils and further demonstrate that MEK-mediated signaling pathways are crucial for SCF-induced CCL6 chemokine activation and eosinophil survival. SCF-mediated eosinophil activation was demonstrated to include PI-3K activation as well as MEK/MAPK phosphorylation pathways. Subsequent analysis of CCL6 gene activation and production induced by SCF in the presence or absence of rather specific inhibitors for certain pathways demonstrated that the MEK/MAPK pathway but not the PI-3K pathway was crucial for the SCF-induced CCL6 gene activation. These same signaling pathways were shown to initiate antiapoptotic events and promote eosinophil survival, including up-regulation of BCL2 and BCL3. Altogether, SCF appears to be a potent eosinophil activation and survival factor.

Biological therapy in the management of recent-onset Crohn's disease: why, when and how?

Crohn's disease is a chronic inflammatory bowel disease that may involve any part of the gastrointestinal tract. Conventional therapy consists of corticosteroids, azathioprine or methotrexate, but the clinical management of Crohn's disease is significantly hampered by adverse effects. With the introduction of biological agents (such as infliximab), the goals of therapy have advanced, including induction of remission with bowel healing as well as reduction in the rate of complications, surgeries and mortality. Current therapy for moderate to severe Crohn's disease is based on 'step-up' algorithms, which initiate treatment with corticosteroids followed by immunomodulatory agents, and defer therapy with biological agents until patients become refractory to conventional therapeutics. Recently, it has been shown that induction therapy with infliximab and azathioprine in recent-onset Crohn's disease (i.e. 'top-down' approach) is superior to current step-up algorithms to induce clinical remission. The underlying molecular mechanisms responsible for these differences in clinical outcome remain to be defined. Experimental studies have demonstrated that corticosteroids are able to induce impaired apoptosis of immune cells, including T cells and dendritic cells, resulting in loss of tolerance and subsequent autoimmunity. Further research will have to determine whether corticosteroid therapy augments the mechanism of loss of tolerance in Crohn's disease, which could complicate future clinical management.

Regulatory T cells as potential immunotherapy in allergy

PURPOSE OF REVIEW

CD4 regulatory T cells are fundamental for the induction and maintenance of immunological tolerance to self and foreign-antigens, including allergens. Here we discuss recent advances in the field of regulatory T cells and how this knowledge can be exploited to treat and prevent allergy.

RECENT FINDINGS

Current research suggest that naturally occurring CD4CD25 regulatory T cells together with inducible IL-10-producing CD4 regulatory T cells actively control allergic responses and that their function or numbers may contribute to the development or progression of allergy. Indeed, successful treatment of allergy by allergen-specific immunotherapy may depend on the induction of IL-10 secreting CD4 T cells. Work has begun to reveal the impact of various pharmaceutical treatments on naturally occurring CD25 regulatory T cells. In addition, recent findings point to an important role for toll-like receptors in the tuning of regulatory T cell function and homeostasis. This may link the hygiene hypothesis to regulatory T cells and open up new possibilities for early intervention in allergic disease.

SUMMARY

The identification of a role for regulatory T cells in allergic disease has provided a host of new therapeutic possibilities, with the potential prospect of safe and long-term alleviation of allergic diseases.

IL-12-induced T-bet expression and IFNgamma release in lymphocytes from asthmatics--role of MAPkinases ERK-1/-2, p38(MAPK) and effect of dexamethasone

The transcription factor T-box-expressed-in-T-cells (T-bet) is required for T(H)1 lymphocyte differentiation, regulates the IL-12-induced expression of the T(H)1-specific cytokine IFNgamma and may be dysregulated in asthmatics. The modulatory role of extracellular signal-regulated kinase (ERK)-1/-2, p38mitogen-activated protein kinase (MAPK) and dexamethasone on IL-12 induced T-bet and IFNgamma expression was assessed in peripheral blood lymphocytes of 10 atopic asthmatics and 10 nonatopic normals. IFNgamma production was dependent on phosphorylation of ERK-1/-2 and p38MAPK, as examined by PD098059, an inhibitor of the upstream activator of MAPKkinase (MKK-1), and SB203580, an inhibitor of p38MAPK. The inhibitory effect of PD098059 on IFNgamma release was decreased in asthmatic T-cells compared with normals. The IL-12-induced T-bet expression and the inhibitory effect of SB203580 were increased in asthmatic T-cells compared with normals. Dexamethasone blocked the IL-12-induced T-bet expression in asthmatic T-cells completely and decreased IL-12-induced IFNgamma release by approximately 50%, which occurred to the same extent in asthmatic and normal T-cells. In conclusion, (1) p38MAPK-pathway rather than ERK-pathway may play a more basic role in the regulation of the increased T-bet expression in asthma, and (2) ERK- and p38MAPK-activation modulate IFNgamma expression independently of T-bet and this regulatory role of ERK-1/-2 on IFNgamma release is impaired in asthma. The therapeutic benefit of dexamethasone on T-bet and IFNgamma production seems to be critical.

Immune dysregulation in asthma

Allergic diseases and asthma are caused by dysregulated Th2-biased immune responses to environmental allergens in genetically predisposed individuals. Over the past several years there has been much progress in understanding the mechanisms by which Th2 responses are generated and the pathogenic role of natural killer T cells in asthma. In addition, there has been much progress in understanding the mechanisms of tolerance to allergens, the role of natural and adaptive allergen-specific regulatory T cells, and the strategies to prevent or to reverse allergic disease and asthma. Impaired expansion of regulatory T cells is hypothesized to lead to the development of allergy and asthma, and treatment to induce allergen-specific regulatory T cells could provide curative therapies for these problems.

Papel das células T reguladoras no desenvolvimento de dermatoses

Células T, em particular as células T CD4+, têm sido associadas a muitos aspectos das doenças de pele. A evidência atual sugere, porém, que o papel dos linfócitos T CD4+ no desenvolvimento de inflamação cutânea excede o de ativador pró-inflamatório das células T de ação que dirigem a resposta imune. Subtipos de células T com capacidade reguladora, tais como Tregs CD4+CD25+high, têm sido identificadas. Observações recentes sugerem que em algumas doenças da pele a função dessas células está modificada. Portanto, o desenvolvimento e a função de Tregs na dermatologia são atualmente um tópico atraente devido a sua importância no controle da resposta do sistema imune contra tumores e doenças infecciosas, bem como inibindo o desenvolvimento de auto-imunidade e alergia. Assim, mecanismos reguladores defeituosos podem permitir a quebra da tolerância imune periférica seguida por inflamação crônica e doença. Detalham-se as anormalidades funcionais e a contribuição de diferentes subtipos de células T reguladoras no desenvolvimento de doenças dermatológicas nesta revisão. Acentuam-se os possíveis alvos terapêuticos e as modificações dos T reguladores causados por imunomoduladores usados no campo da dermatologia.