Regulatory T cells negatively regulate neovasculature of airway remodeling via DLL4-Notch signaling

Regulatory T cells in lung disease and transplantation

Pulmonary disease can refer to the disease of the lung itself or the pulmonary manifestations of systemic diseases, which are often connected to the malfunction of the immune system. Regulatory T (Treg) cells have been shown to be important in maintaining immune homeostasis and preventing inflammatory damage, including lung diseases. Given the increasing amount of evidence linking Treg cells to various pulmonary conditions, Treg cells might serve as a therapeutic strategy for the treatment of lung diseases and potentially promote lung transplant tolerance. The most potent and well-defined Treg cells are Foxp3-expressing CD4+ Treg cells, which contribute to the prevention of autoimmune lung diseases and the promotion of lung transplant rejection. The protective mechanisms of Treg cells in lung disease and transplantation involve multiple immune suppression mechanisms. This review summarizes the development, phenotype and function of CD4+Foxp3+ Treg cells. Then, we focus on the therapeutic potential of Treg cells in preventing lung disease and limiting lung transplant rejection. Furthermore, we discussed the possibility of Treg cell utilization in clinical applications. This will provide an overview of current research advances in Treg cells and their relevant application in clinics.

CD4+CD25+FOXP3+ regulatory T cells: a potential "armor" to shield "transplanted allografts" in the war against ischemia reperfusion injury

Despite the advances in therapeutic interventions, solid organ transplantation (SOT) remains the "gold standard" treatment for patients with end-stage organ failure. Recently, vascularized composite allotransplantation (VCA) has reemerged as a feasible treatment option for patients with complex composite tissue defects. In both SOT and VCA, ischemia reperfusion injury (IRI) is inevitable and is a predominant factor that can adversely affect transplant outcome by potentiating early graft dysfunction and/or graft rejection. Restoration of oxygenated blood supply to an organ which was previously hypoxic or ischemic for a period of time triggers cellular oxidative stress, production of both, pro-inflammatory cytokines and chemokines, infiltration of innate immune cells and amplifies adaptive alloimmune responses in the affected allograft. Currently, Food and Drug Administration (FDA) approved drugs for the treatment of IRI are unavailable, therefore an efficacious therapeutic modality to prevent, reduce and/or alleviate allograft damages caused by IRI induced inflammation is warranted to achieve the best-possible transplant outcome among recipients. The tolerogenic capacity of CD4+CD25+FOXP3+ regulatory T cells (Tregs), have been extensively studied in the context of transplant rejection, autoimmunity, and cancer. It was not until recently that Tregs have been recognized as a potential cell therapeutic candidate to be exploited for the prevention and/or treatment of IRI, owing to their immunomodulatory potential. Tregs can mitigate cellular oxidative stress, produce anti-inflammatory cytokines, promote wound healing, and tissue repair and prevent the infiltration of pro-inflammatory immune cells in injured tissues. By using strategic approaches to increase the number of Tregs and to promote targeted delivery, the outcome of SOT and VCA can be improved. This review focuses on two sections: (a) the therapeutic potential of Tregs in preventing and mitigating IRI in the context of SOT and VCA and (b) novel strategies on how Tregs could be utilized for the prevention and/or treatment of IRI.

Treg specialization and functions beyond immune suppression

The actions of the immune system are finely tuned, involving complex communication and coordination between diverse immune and non-immune cells across the tissues of the body. A healthy immune system requires a precise balance between immunity and tolerance. Regulatory T cells (Tregs) have long been appreciated as one of the master regulators of this balance; their importance is underscored by the autoimmunity that develops in mice and humans when Tregs are missing or dysfunctional. In addition to the immunoregulatory roles of Tregs in suppressing autoimmunity and inflammation via control of adaptive and innate immune responses, several non-immune modulatory functions of Tregs have been identified in recent years. In this review, we have highlighted the growing literature on the action of Tregs in metabolism, stem cell maintenance, tissue repair, and angiogenesis. Alongside Tregs' immune suppressive role, these non-suppressive activities comprise a key function of Tregs in regulating health and disease. As Tregs receive increasing attention as therapeutic targets, understanding their non-canonical functions may become an important feature of Treg-directed interventions.

The Role of Sex in Acute and Chronic Liver Damage

Acute and chronic hepatic damages are caused by xenobiotics or different diseases affecting the liver, characterized by different etiologies and pathological features. It has been demonstrated extensively that liver damage progresses differently in men and women, and some chronic liver diseases show a more favorable prognosis in women than in men. This review aims to update the most recent advances in the comprehension of the molecular basis of the sex difference observed in both acute and chronic liver damage. With this purpose, we report experimental studies on animal models and clinical observations investigating both acute liver failure, e.g., drug-induced liver injury (DILI), and chronic liver diseases, e.g., viral hepatitis, alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), autoimmune liver diseases, and hepatocellular carcinoma (HCC).

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

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

γδT17/γδTreg cell subsets: a new paradigm for asthma treatment

Bronchial asthma (abbreviated as asthma), is a heterogeneous disease characterized by chronic airway inflammation and airway hyperresponsiveness. The main characteristics of asthma include variable reversible airflow limitation and airway remodeling. The pathogenesis of asthma is still unclear. Th1/Th2 imbalance, Th1 deficiency and Th2 hyperfunction are classic pathophysiological mechanisms of asthma. Some studies have shown that the imbalance of the Th1/Th2 cellular immune model and Th17/Treg imbalance play a key role in the occurrence and development of asthma; however, these imbalances do not fully explain the disease. In recent years, studies have shown that γδT and γδT17 cells are involved in the pathogenesis of asthma. γδTreg has a potential immunosuppressive function, but its regulatory mechanisms have not been fully elucidated. In this paper, we reviewed the role of γδT17/γδTreg cells in bronchial asthma, including the mechanisms of their development and activation. Here we propose that γδT17/Treg cell subsets contribute to the occurrence and development of asthma, constituting a novel potential target for asthma treatment.

Regulatory T Cells in Angiogenesis

Regulatory T cells (Tregs) are crucial mediators of immune homeostasis. They regulate immune response by suppressing inflammation and promoting self-tolerance. In addition to their immunoregulatory role, a growing body of evidence highlights the dynamic role of Tregs in angiogenesis, the process of forming new blood vessels. Although angiogenesis is critically important for normal tissue regeneration, it is also a hallmark of pathological processes, including malignancy and chronic inflammation. Interestingly, the role of Tregs in angiogenesis has been shown to be highly tissue- and context-specific and as a result can yield either pro- or antiangiogenic effects. For these reasons, there is considerable interest in determining the molecular underpinnings of Treg-mediated modulation of angiogenesis in different disease states. The present review summarizes the role of Tregs in angiogenesis and mechanisms by which Tregs regulate angiogenesis and discusses how these mechanisms differ in homeostatic and pathological settings.

An emerging role of regulatory T-cells in cardiovascular repair and regeneration

Accumulating evidence has demonstrated that immune cells play an important role in the regulation of tissue repair and regeneration. After injury, danger signals released by the damaged tissue trigger the initial pro-inflammatory phase essential for removing pathogens or cellular debris that is later replaced by the anti-inflammatory phase responsible for tissue healing. On the other hand, impaired immune regulation can lead to excessive scarring and fibrosis that could be detrimental for the restoration of organ function. Regulatory T-cells (Treg) have been revealed as the master regulator of the immune system that have both the immune and regenerative functions. In this review, we will summarize their immune role in the induction and maintenance of self-tolerance; as well as their regenerative role in directing tissue specific response for repair and regeneration. The latter is clearly demonstrated when Treg enhance the differentiation of stem or progenitor cells such as satellite cells to replace the damaged skeletal muscle, as well as the proliferation of parenchymal cells including neonatal cardiomyocytes for functional regeneration. Moreover, we will also discuss the reparative and regenerative role of Treg with a particular focus on blood vessels and cardiac tissues. Last but not least, we will describe the ongoing clinical trials with Treg in the treatment of autoimmune diseases that could give clinically relevant insights into the development of Treg therapy targeting tissue repair and regeneration.

Green propolis increases myeloid suppressor cells and CD4+Foxp3+ cells and reduces Th2 inflammation in the lungs after allergen exposure

ETHNOPHARMACOLOGICAL RELEVANCE

Propolis is a natural product produced by honeybees used as a medicine at least to 300 BC. In the last decades, several studies showed biological and pharmacological properties of propolis, witch scientifically explains the empirical use for centuries. The anti-inflammatory activity of propolis with the purpose to reduce Th2 inflammation has been evaluated in allergic asthma. However, it remains to be determined how propolis negatively regulates the immune response after allergen re-exposure.

AIM OF THE STUDY

We hypothesized that the anti-inflammatory activity of propolis is dependent on the induction of myeloid derived suppressor cells (MDSC) and regulatory T cells.

MATERIALS AND METHODS

To assess this hypothesis, we used an ovalbumin-induced asthma model to evaluate the effect of EPP-AF® dry extract from Brazilian green propolis.

RESULTS

Propolis treatment decreased pulmonary inflammation and mucus production as well as eosinophils and IL-5 in the broncoalveolar lavage. Propolis enhanced also in vitro differentiation and in vivo frequency of lung MDSC and CD4⁺Foxp3⁺ regulatory T cells.

CONCLUSIONS

Together these results confirm the immunomodulatory potential of propolis during sensitization and challenge with allergen. In addition, the collecting findings show, for the first time, that propolis increases the frequency of MDSC and CD4⁺Foxp3⁺ regulatory T cells in the lungs, and suggest that it could be use as target for development of new immunotherapy or adjuvant immunotherapy for asthma.

Elevated Th17 cell frequencies and Th17/Treg ratio are associated with airway hyperresponsiveness in asthmatic children

Introduction: The elevation of T helper (Th)17 cell frequencies and the imbalance of Th17/regulatory T (Treg) cells occur in asthma pathogenesis. Airway hyperresponsiveness (AHR) is a cardinal feature of asthma, and Th17 responses can promote AHR. We hypothesized that changes in Th17 cells and the Th17/Treg ratio correlate with AHR in asthmatic children.Methods: Twenty asthmatic children and twenty healthy children were included in the study. The peak expiratory flow (PEF) % pred, forced expiratory volume in 1 s (FEV₁) % pred and the FEV₁/forced vital capacity (FVC) ratio were measured in all subjects. Methacholine challenge test (MCT) was performed in asthmatic children. Flow cytometric analysis was used to determine the proportions of Th17 and Treg cells in peripheral blood mononuclear cells. ELISA was used to assess serum levels of interleukin (IL)-17A and IL-10.Results: Th17 cell frequencies (2.272 ± 0.207% in asthmatics, 1.193 ± 0.131% in controls, P < 0.01) and Th17/Treg ratios (0.371 ± 0.0387 in asthmatics, 0.183 ± 0.020 in controls, P < 0.01) were significantly increased in asthmatic children compared to controls. In asthmatic children, the MCT grade had positive correlations with the Th17 cell frequencies [r = 0.718, P < 0.01], serum IL-17A level [r = 0.753, P < 0.01] and Th17/Treg ratio [r = 0.721, P < 0.01], while the log₁₀PD20-FEV₁ value was negatively correlated with the Th17 cell frequencies [r = -0.654, P < 0.01], serum IL-17A level [r = -0.652, P < 0.01] and Th17/Treg ratio [r = -0.625, P < 0.01].Conclusion: Th17 cell, IL-17A and Th17/Treg ratio were positively correlated with AHR in asthmatic children. It may be helpful to monitor Th17 cells and the Th17/Treg ratio as indicators of AHR in clinical practice.

Dysfunctional and Proinflammatory Regulatory T-Lymphocytes Are Essential for Adverse Cardiac Remodeling in Ischemic Cardiomyopathy

BACKGROUND

Heart failure (HF) is a state of inappropriately sustained inflammation, suggesting the loss of normal immunosuppressive mechanisms. Regulatory T-lymphocytes (Tregs) are considered key suppressors of immune responses; however, their role in HF is unknown. We hypothesized that Tregs are dysfunctional in ischemic cardiomyopathy and HF, and they promote immune activation and left ventricular (LV) remodeling.

METHODS

Adult male wild-type C57BL/6 mice, Foxp3-diphtheria toxin receptor transgenic mice, and tumor necrosis factor (TNF) α receptor-1 (TNFR1)^-/- mice underwent nonreperfused myocardial infarction to induce HF or sham operation. LV remodeling was assessed by echocardiography as well as histological and molecular phenotyping. Alterations in Treg profile and function were examined by flow cytometry, immunostaining, and in vitro cell assays.

RESULTS

Compared with wild-type sham mice, CD4⁺Foxp3⁺ Tregs in wild-type HF mice robustly expanded in the heart, circulation, spleen, and lymph nodes in a phasic manner after myocardial infarction, beyond the early phase of wound healing, and exhibited proinflammatory T helper 1-type features with interferon-γ, TNFα, and TNFR1 expression, loss of immunomodulatory capacity, heightened proliferation, and potentiated antiangiogenic and profibrotic properties. Selective Treg ablation in Foxp3-diphtheria toxin receptor mice with ischemic cardiomyopathy reversed LV remodeling and dysfunction, alleviating hypertrophy and fibrosis, while suppressing circulating CD4⁺ T cells and systemic inflammation and enhancing tissue neovascularization. Tregs reconstituted after ablation exhibited restoration of immunosuppressive capacity and normalized TNFR1 expression. Treg dysfunction was also tightly coupled to Treg-endothelial cell contact- and TNFR1-dependent inhibition of angiogenesis and the mobilization and tissue infiltration of CD34⁺Flk1⁺ circulating angiogenic cells in a C-C chemokine ligand 5/C-C chemokine receptor 5-dependent manner. Anti-CD25-mediated Treg depletion in wild-type mice imparted similar benefits on LV remodeling, circulating angiogenic cells, and tissue neovascularization.

CONCLUSIONS

Proinflammatory and antiangiogenic Tregs play an essential pathogenetic role in chronic ischemic HF to promote immune activation and pathological LV remodeling. The restoration of normal Treg function may be a viable approach to therapeutic immunomodulation in this disease.

Multi-Faceted Notch in Allergic Airway Inflammation

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

Acupuncture Regulates the Balance of CD4+ T Cell Subtypes in Experimental Asthma Mice

OBJECTIVE

To evaluate the involvement of different CD4⁺ T cell subtypes in the anti-asthmatic effects of acupuncture in asthmatic mice.

METHODS

BALB/c mice were challenged by ovalbumin (OVA) for the establishment of experimental asthma model. Mice were divided into 4 groups by a random number table including the normal control, asthma model, acupuncture and sham acupuncture groups (14 per group). Acupoints Dazhui (GV 14), bilateral Fengmen (BL 12) and Feishu (BL 13) were selected for manual acupuncture treatment every other day for 4 weeks and Huantiao (GB 30) was selected for sham acupuncture. Airway hyperresponsiveness was examined by Buxco Pulmonary System. Pulmonary histopathology analysis was performed for inflammatory cell infiltration and mucus hypersecretion by haematoxylin eosin staining and periodic acid-Schiffstaining. Inflammatory mediators assays of serum were investigated by enzyme-linked immunosorbent assay and Bio-Plex. CD4⁺ T cell subpopulations including the expression levels of important factors in T lymphocyte polarization in lung tissue were examined by flow cytometric and Western blot analyses. Related pathways were detected by Western blot assay.

RESULTS

Compared with the OVA-induced asthma model group, acupuncture could attenuate airway hyperresponsiveness, inhibit inflammatory cell infiltration and mucus hypersecretion (P<0.05 or P<0.01). Furthermore, acupuncture increased the expressions of T-bet and Foxp3⁺, the cell numbers of CD4⁺ interferon gamma (IFN-γ)⁺ and CD4⁺ Foxp3⁺ in lung tissue and the level of Treg type cytokine interleukin (IL)-10 in serum (P<0.05 or P<0.01). Meanwhile, acupuncture reduced the RAR-related orphan receptor gamma t (RORγt) level, the cell numbers of CD4⁺ IL-17A⁺ as well as the levels of IL-5, IL-13 and IL-17A in serum (P<0.05 or P<0.01). In addition, both acupuncture and sham acupuncture could inhibit the phosphorylation of p38 and p44/42 (P<0.01).

CONCLUSION

Acupuncture could alleviate allergic airway inflammation by strengthening the activities of Th1 and Treg, thus regulating the balance of CD4⁺ T cell subtypes in experimental asthmatic mice.

Sexual dimorphism in hepatitis B and C and hepatocellular carcinoma

The incidence of viral hepatitis B or C (HBV/HCV) infection and hepatocellular carcinoma is higher in male compared to female populations, showing a faster disease progression and results in a worse overall survival. Indeed, women are in general better protected from viral infections and show a lower risk of death from malignant cancer in comparison to men. Females mount stronger innate and adaptive immune responses than males, and therefore, most of the autoimmune diseases occur predominantly in females. Next to occupational and/or behavioral factors, cellular and molecular differences between the two sexes contribute to this observation. In this review, we will discuss underlying mechanisms that are important for the observed sex-related differences in liver diseases. A better appreciation of these differences between the two sexes might be of value for better and gender-specific treatment options.

Anti-Dll4 Antibody Inhibits the Differentiation of Th17 Cells in Asthmatic Mice

T helper 17 (Th17) cells play an important role in allergic asthma, and the Notch ligand Delta-like ligand (Dll)4 has been reported to direct the differentiation of Th17 cells. In this study, experimental animals were divided into five groups (control group, asthma group, physiological saline group, anti-Dll4 antibody group, and immunoglobulin G group). The study aimed to explore the effect of anti-Dll4 antibody on the differentiation of Th17 cell in asthmatic mice. Dll4 protein expressions were performed by immunohistochemical imaging. The proportion of Th17 cells in mouse spleen-isolated CD4⁺ T cells were measured by flow cytometry. The protein expression of Th17 transcription factor retinoid-related orphan nuclear receptor (RORγt) was detected by Western blotting. Interleukin (IL)-17 levels in serum were measured by enzyme-linked immunosorbent assay (ELISA). The study found that the expression of Dll4 in lung tissue from the asthma group significantly increased compared with the anti-Dll4 antibody group. The ratio of Th17 cells in CD4⁺ T cells was significantly downregulated, and the protein expression of ROR_γt in spleen significantly reduced in the anti-Dll4 antibody group compared with the asthma group. Moreover, the IL-17 level in serum from the anti-Dll4 antibody group significantly reduced compared with the asthma group. These results suggested that anti-Dll4 antibody could inhibit the differentiation of Th17 cells in asthmatic mice.

Endothelial cells in the innate response to allergens and initiation of atopic asthma

Protease-activated receptor 2 (PAR-2), an airway epithelial pattern recognition receptor (PRR), participates in the genesis of house dust mite-induced (HDM-induced) asthma. Here, we hypothesized that lung endothelial cells and proangiogenic hematopoietic progenitor cells (PACs) that express high levels of PAR-2 contribute to the initiation of atopic asthma. HDM extract (HDME) protease allergens were found deep in the airway mucosa and breaching the endothelial barrier. Lung endothelial cells and PACs released the Th2-promoting cytokines IL-1α and GM-CSF in response to HDME, and the endothelium had PAC-derived VEGF-C-dependent blood vessel sprouting. Blockade of the angiogenic response by inhibition of VEGF-C signaling lessened the development of inflammation and airway remodeling in the HDM model. Reconstitution of the bone marrow in WT mice with PAR-2-deficient bone marrow also reduced airway inflammation and remodeling. Adoptive transfer of PACs that had been exposed to HDME induced angiogenesis and Th2 inflammation with remodeling similar to that induced by allergen challenge. Our findings identify that lung endothelium and PACs in the airway sense allergen and elicit an angiogenic response that is central to the innate nonimmune origins of Th2 inflammation.

Notch Signaling: Linking Embryonic Lung Development and Asthmatic Airway Remodeling

Lung development is mediated by assorted signaling proteins and orchestrated by complex mesenchymal-epithelial interactions. Notch signaling is an evolutionarily conserved cell-cell communication mechanism that exhibits a pivotal role in lung development. Notably, both aberrant expression and loss of regulation of Notch signaling are critically linked to the pathogenesis of various lung diseases, in particular, pulmonary fibrosis, lung cancer, pulmonary arterial hypertension, and asthmatic airway remodeling; implying that precise regulation of intensity and duration of Notch signaling is imperative for appropriate lung development. Moreover, evidence suggests that Notch signaling links embryonic lung development and asthmatic airway remodeling. Herein, we summarized all-recent advances associated with the mechanistic role of Notch signaling in lung development, consequences of aberrant expression or deletion of Notch signaling in linking early-impaired lung development and asthmatic airway remodeling, and all recently investigated potential therapeutic strategies to treat asthmatic airway remodeling.

Notch Ligand DLL4 Alleviates Allergic Airway Inflammation via Induction of a Homeostatic Regulatory Pathway

Notch is a pleiotropic signaling family that has been implicated in pathogenesis of allergic airway diseases; however, the distinct function of individual Notch ligands remains elusive. We investigated whether Notch ligands, Jagged1 and DLL4, exert differential effects in OVA-induced allergic asthma. We found that whilst Jagged1 inhibition mitigated Th2-dominated airway inflammation, blockage of DLL4 aggravated the Th2-mediated asthma phenotypes. Additionally, Jagged1 signaling blockage enhanced IL-17 production and neutrophilic airway infiltration. In vitro, exogenous Jagged1 induced Th2-skewed responses, whereas augmented DLL4 signaling displayed a dual role by promoting expansion of both Tregs and Th17. In vivo, DLL4 blockage impaired Treg differentiation which plausibly resulted in exaggerated asthma phenotypes. On the contrary, administration of DLL4-expressing antigen-presenting cells promoted endogenous Treg expansion and ameliorated the allergic responses. Therefore, whilst Jagged1 induces Th2-skewed inflammation, DLL4 elicits an essential self-regulatory mechanism via Treg-mediated pathway that counterbalances Jagged1-induced Th2 responses and facilitates resolution of the airway inflammation to restore homeostasis. These findings uncover a disparate function of Jagged1 and DLL4 in allergic airway diseases, hinting feasibility of Notch ligand-specific targeting in therapy of allergic airway diseases.

Folate deficiency affects dendritic cell function and subsequent T helper cell differentiation

Insufficient folate status may be related to the increasing prevalence of immune- or inflammation-related chronic diseases. To investigate the effects of folate on immune regulation, we examined the impact of folate deficiency (FD) on dendritic cell (DC) maturation and function and, thus, T helper (Th) cells differentiation. First, bone marrow-derived DCs (BMDCs) were generated from BALB/c mice bone marrow cells cultured in folate-containing (F-BMDCs) or folate-deficient (FD-BMDCs) medium. FD-BMDC displayed more immature phenotype including reduced levels of major histocompatibility complex class II (MHC II), co-stimulatory molecules and characteristic of higher endocytic activity. FD-BMDC produced less IL-12p70 and proinflammatory cytokines in response to lipopolysaccharide. This aberrant DC maturation due to FD resulted in reduced BMDC-induced Th cell activity and lower IL-2, IFNγ, IL-13 and IL-10 productions. Further in vivo study confirmed significantly lower IFNγ and IL-10 productions by T cells and showed higher splenic naïve Th and lower memory T, effector T and regulatory T cell (Treg) percentages in mice fed with the FD diet for 13 weeks. To investigate the role of DCs on T cell activity, splenic DCs (spDC) from FD mice were cocultured with Th cells. The FD spDC had lower MHC II and CD80 expressions and subsequently impaired DC-induced Th differentiation, shown as decreased cytokine productions. This study demonstrated that folate deficiency impaired DC functions and, thus, Th differentiation and responses, suggesting that folate plays a crucial role in maintaining Th cells homeostasis.

Activin-A is overexpressed in severe asthma and is implicated in angiogenic processes

Activin-A is a pleiotropic cytokine that regulates allergic inflammation. Its role in the regulation of angiogenesis, a key feature of airways remodelling in asthma, remains unexplored. Our objective was to investigate the expression of activin-A in asthma and its effects on angiogenesis in vitro.Expression of soluble/immunoreactive activin-A and its receptors was measured in serum, bronchoalveolar lavage fluid (BALF) and endobronchial biopsies from 16 healthy controls, 19 patients with mild/moderate asthma and 22 severely asthmatic patients. In vitro effects of activin-A on baseline and vascular endothelial growth factor (VEGF)-induced human endothelial cell angiogenesis, signalling and cytokine release were compared with BALF concentrations of these cytokines in vivo.Activin-A expression was significantly elevated in serum, BALF and bronchial tissue of the asthmatics, while expression of its protein receptors was reduced. In vitro, activin-A suppressed VEGF-induced endothelial cell proliferation and angiogenesis, inducing autocrine production of anti-angiogenic soluble VEGF receptor (R)1 and interleukin (IL)-18, while reducing production of pro-angiogenic VEGFR2 and IL-17. In parallel, BALF concentrations of soluble VEGFR1 and IL-18 were significantly reduced in severe asthmatics in vivo and inversely correlated with angiogenesis.Activin-A is overexpressed and has anti-angiogenic effects in vitro that are not propagated in vivo, where reduced basal expression of its receptors is observed particularly in severe asthma.

Lymph node trafficking of regulatory T cells is prerequisite for immune suppression

Regulatory T cells have a crucial role in health and disease because of their immune regulation function. However, the anatomic sites where regulatory T cells exert optimal immune regulation are open to debate. In our current study with the use of a shear-stress flow assay, we found that regulatory T cells exhibited significantly decreased adhesion to either activated endothelial monolayer or intercellular adhesion molecule 1 or E-selectin-coated surfaces compared with activated effector T cells. The less transmigration capacity of the regulatory T cells prompted our speculation of preferential lymph node localization for the regulatory T cells that endowed these cells with immune regulation function in the most efficient manner. To test this hypothesis, the role of lymph node localization in regulatory T cell-mediated immune suppression was evaluated with a footpad inflammation model. We found that adoptively transferred regulatory T cells inhibited the development of footpad inflammation. In addition, although blockage of CCR7 or CD62L had no effect on the immune suppressive function of the regulatory T cells per se, pretreatment of the regulatory T cells with either CCR7 or CD62L blocking antibodies prevented their recruitment into draining lymph nodes and concomitantly abrogated the immune suppressive effects of adoptively transferred regulatory T cells during footpad inflammation. Our data demonstrate the crucial role of lymph node localization in regulatory T cell-mediated immune suppression and suggest a probable hierarchy in the anatomic sites for optimal immune regulation. Elucidating the relationships between the transmigration characteristics of the regulatory T cells and their immune regulation function will provide insightful information for regulatory T cell-based cell therapy.

Dll4 in the DCs isolated from OVA-sensitized mice is involved in Th17 differentiation inhibition by 1,25-dihydroxyvitamin D3 in vitro

INTRODUCTION

T helper 17 cell (Th17) cells play an important role in neutrophilic asthma, and 1,25(OH)2D3 has been reported to modulate the proliferation and differentiation of T cells. In this study, we examined the effects of 1,25(OH)2D3 on the dendritic cell (DC)-mediated regulation of Th17differentiation from OVA-sensitized mice.

METHODS

DCs were isolated from ovalbumin-sensitized mouse spleens. Lipopolysaccharide (LPS) was administered to stimulate the DCs for 24 h, and dexamethasone or 1,25(OH)2D3 was applied simultaneously. The expression of Notch ligand delta-like ligand 4 (Dll4) in the DCs was detected in each group. All the groups of treated DCs were co-cultured with T cells, and Dll4 was inhibited in these groups. After 24 h, Th17 and Treg cell differentiation and the IL-17A levels were measured.

RESULTS

Dll4 expression was increased in LPS-treated DCs compared with the control group (p = 0.05), resulting in increased Th17 cell differentiation (p = 0.002). Treatment with 1,25(OH)2D3 inhibited the Dll4 expression(p = 0.04) and decreased Th17 cell differentiation (p = 0.001) in DCs that was induced by LPS. Directly inhibiting Dll4 reduced Th17 cell differentiation, and Th17 cell differentiation was not further inhibited by 1,25(OH)2D3 once Dll4 was blocked.

CONCLUSIONS

These result suggest that Dll4 in the DCs isolated from OVA-sensitized mice is involved in Th17 differentiation inhibition by 1,25(OH)2D3.

The immunology of asthma

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

Inactivation of Notch signaling reverses the Th17/Treg imbalance in cells from patients with immune thrombocytopenia

T helper 17 (Th17) cells and regulatory T (Treg) cells, along with Th1 and Th2 cells, may contribute to the development of immune thrombocytopenia (ITP). The imbalance of Th17/Treg toward Th17 cells has been shown to play a pivotal role in the peripheral immune response. Notch signaling has been implicated in peripheral T-cell activation and effector cell differentiation. However, the role of Th17/Treg in the pathogenesis of ITP and the effect of Notch signaling on Th17/Treg imbalances remain largely elusive in ITP. In vitro, we treated peripheral blood mononuclear cells (PBMCs) from ITP and healthy controls with γ-secretase inhibitor (DAPT). Th17 cells and Treg cells were measured by flow cytometry and IL-17, IL-21, and IL-10 secretion by enzyme immunoassay technique. The mRNA expression of Ntoch1, Hes1, Hey1, RORγt, and Foxp3 was investigated by RT-PCR. Cell proliferation and apoptosis were determined by the Cell Counting Kit-8 and apoptosis detection kit. We demonstrated that DAPT was effective in inhibiting mRNA expression of Notch signaling molecules. In untreated cultured PBMCs from ITP patients, we observed elevated Th17 cell and IL-21 levels and RORγt mRNA expression, decreased Treg cells and Foxp3 mRNA expression, and an increased ratio of Th17/Treg and RORγt/Foxp3. After inactivating Notch signal by DAPT, Th17 cells and Th17/Treg ratio were dose dependently decreased and accompanied by the reduction of IL-17 in culture supernatants and RORγt mRNA expression in ITP patients. However, no significant difference was found for Treg cells and Foxp3 mRNA expression, RORγt/Foxp3 ratio, and IL-21 and IL-10 levels after DAPT treatment in ITP patients. We also present evidence that the effect of DAPT inhibition on the Th17 cell response was associated with downregulation of RORγt and IL-17 transcription using human in vitro polarization. In conclusion, our findings highlight the importance of Notch signaling in Th17/Treg imbalances in ITP. Inactivation of Notch signaling might be a potential immunoregulatory strategy in ITP patients.

Clinical role of Notch signaling pathway in intraductal papillary mucinous neoplasm of the pancreas

BACKGROUND AND AIM

This study was performed to elucidate the expression of the Notch signaling pathway and its correlations to clinicopathological factors of intraductal papillary mucinous neoplasms (IPMNs). It is incontrovertible that regulatory T cells (Tregs) play an important role in tumor immunity. However, the whole mechanism of control of peripheral Tregs remains unclear. It is also known that the Notch signaling pathway is involved in Treg suppressor function. Moreover, IPMNs have a high malignant potential.

METHODS

Peripheral blood samples and resected specimens from 18 patients with IPMN were evaluated. All patients were pathologically diagnosed with IPMN. Resected specimens were immunohistochemically evaluated (anti-Notch1, anti-Notch2, and anti-Notch2-intracellular domain antibody staining) and compared in terms of clinicopathological factors. Peripheral Treg populations were analyzed with an automated flow cytometer.

RESULTS

Disease-free survival was significantly worse in the Notch1 high-expression group (P = 0.023). Notch2 family expressions were higher in intraductal papillary mucinous carcinoma (IPMC) than in intraductal papillary mucinous adenoma (IPMA) (Notch2, P = 0.012; Notch2-intracellular domain, P = 0.036). Jagged1 expression was significantly higher in IPMC than in IPMA (P < 0.05) and was significantly related to recurrence. The Treg population in peripheral blood was higher in patients with IPMC than in those with IPMA (P < 0.01).

CONCLUSIONS

Notch signaling, especially Jagged1 expression, reflects IPMN aggressiveness. Our data may suggest that the Notch signaling pathway is a key pathway that determines IPMN pathological aggressiveness and reflects the peripheral Treg population.

Asthma is not only an airway disease, but also a vascular disease

Multiple studies have identified an expansion and morphological dysregulation of the bronchial vascular network in the airways of asthmatics. Increased number, size and density of blood vessels, as well as vascular leakage and plasma engorgement, have been reported in the airways of patients with all grades of asthma from mild to fatal. This neovascularisation is an increasingly commonly reported feature of airway remodelling; however, the pathophysiological impact of the increased vasculature in the bronchial wall and its significance to pulmonary function in asthma are unrecognised at this time. Multiple factors capable of influencing the development and persistence of the vascular network exist within asthmatic airway tissue. These include structural components of the altered extracellular matrix (ECM), imbalance of proteases and their endogenous inhibitors, release of active matrikines and the dysregulated levels of both soluble and matrix sequestered growth factors. This review will explore the features of the asthmatic airway which influence the development and persistence of the increased vascular network, as well as the effect of enhanced tissue perfusion on chronic inflammation and airway dynamics. The response of cells of the airways to the altered vascular profile and the subsequent influence on the features of airway remodelling will also be highlighted. We will explore the failure of current asthma therapeutics in "normalising" this vascular remodelling. Finally, we will summarize the outcomes of recent clinical trials which provide hope that anti-angiogenic therapies may be a potent asthma-resolving class of drugs and provide a new approach to asthma management in the future.

Asthma: the importance of dysregulated barrier immunity

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

Notch signaling and T-helper cells in EAE/MS

The Notch signaling pathway preservation across species hints to the indispensable role it plays during evolution. Over the last decade the science community has extensively studied the Notch signaling pathway, with Notch emerging as a key player in embryogenesis, tissue homeostasis, angiogenesis, and immunoregulation. Multiple sclerosis (MS) is an incurable yet treatable autoimmune chronic inflammatory disease of the central nervous system. The aim of this review is to provide a brief description of the Notch signaling pathway, and summarize the current literature implicating Notch in the pathogenesis of MS.

Notch ligand delta-like 4-pretreated dendritic cells alleviate allergic airway responses by enhancing IL-10 production

The Notch pathway plays a role in the processes of cell proliferation, differentiation, and apoptosis, which affect the development and function of various organs. Dendritic cells (DCs), as professional antigen-presenting cells (APCs), induce T cell activation and promote T cell differentiation by antigen stimulation. Research has shown that Notch ligand delta-like 4 (Dll4) in APCs is associated with stimulation of a Th1-type response. However, the regulatory roles of Dll4 in the activation and function of DCs have yet to be clearly elucidated. In this study, we demonstrated that activation of Dll4-pretreated bone marrow-derived DCs by performing ovalbumin (OVA) stimulation expressed a high level of interleukin (IL)-10 without diminishing IL-12 production. By contrast, the proinflammatory cytokines, IL-1β, IL-6, and tumor necrosis factor (TNF)-α, decreased in Dll4-pretreated DCs by performing either lipopolysaccharide (LPS) or OVA stimulation. Compared to fully mature DCs, lower levels of MHC class II CD40 and higher levels of CD80 and CD86 molecules were expressed in these semi-mature like DCs. Dll4 Notch signaling also enhanced Notch ligand mRNA expression of Dll1, Dll4, and Jagged1 in DCs. Dll4-modified DCs exhibited a reduced capacity to stimulate the proliferation of OVA-specific CD4(+) T cells, but actively promoted large amounts of IL-10 production in these activated T cells. Furthermore, immunomodulatory effects of Dll4-modified DCs were examined in an established asthmatic animal model. After adoptive transfer of OVA-pulsed plus Dll4-pretreated DCs in OVA-immunized mice, OVA challenge induced lower OVA-specific immunoglobulin E (IgE) and higher IgG2a antibody production, lower eotaxin, keratinocyte-derived chemokine (KC), IL-5, and IL-13 release in bronchial alveolar lavage fluid, attenuated airway hyper-responsiveness, and promoted higher IL-10 and interferon (IFN)-γ production in the spleen. In summary, our findings elucidate the new role of Dll4 in the phenotype and function of DCs and provide a novel approach for manipulating T cell-driven deleterious immune diseases.

CD4+CD25+Foxp3+ T cells contribute to the antiasthmatic effects of Astragalus membranaceus extract in a rat model of asthma

Astragalus membranaceus (AM), a traditional Chinese medicinal herb, has been widely used for centuries to treat asthma in China. Previous studies demonstrated that AM had inhibitory effects on airway hyperresponsiveness, inflammation and airway remodeling in murine models of asthma. However, it remained unclear whether the beneficial effects of AM on asthma were associated with CD4(+)CD25(+)Foxp3(+) Treg cells; this issue is the focus of the present work. An asthma model was established in Sprague-Dawley (SD) rats that were sensitized and challenged with ovalbumin. Bronchoalveolar lavage fluid (BALF) was assessed for inflammatory cell counts and cytokine levels. Airway hyperresponsiveness was detected by direct airway resistance analysis. Lung tissues were examined for cell infiltration, mucus hypersecretion and airway remodeling. CD4(+)CD25(+)Foxp3(+) Treg cells in the BALF and Foxp3 mRNA expression in lung tissues were examined. The oral administration of AM significantly reduced airway hyperresponsiveness to aerosolized methacholine and inhibited eosinophil counts and reduced IL-4, IL-5 and IL-13 levels and increased INF-γ levels in the BALF. Histological studies showed that AM markedly decreased inflammatory infiltration, mucus secretion and collagen deposition in the lung tissues. Notably, AM significantly increased population of CD4(+)CD25(+)Foxp3(+) Treg cells and promoted Foxp3(+) mRNA expression in a rat model of asthma. Together, these results suggest that the antiasthmatic effects of AM are at least partially associated with CD4(+)CD25(+)Foxp3(+) Tregs.

Immunomodulatory effects of feeding with Bifidobacterium longum on allergen-induced lung inflammation in the mouse

BACKGROUND

The intestinal microbiota has important effects on host immune responses and feeding with certain commensal organisms has anti-inflammatory effects in a variety of diseases, including experimental asthma. The aim of the current study was to examine how robust the effects of feeding with the commensal strain, Bifidobacterium longum (Bif) were on the pulmonary responses to allergen sensitization and challenge.

METHODS

BALB/c mice were given two intraperitoneal injections of ovalbumin (10 μg in alum) on days 0 and 7 and were fed daily with Bif or vehicle from days 0-14. Challenges with ovalbumin (10 μg) were administered intra-nasally once on day 14 or three times on days 14, 15 and 16 and the lung inflammatory response was assessed one day later.

RESULTS

Bif feeding attenuated airway inflammation following a single ovalbumin challenge, reducing bronchoalveolar lavage (BAL) eosinophilia, BAL fluid IL-4 protein and BAL cell IL-4 and IFN-γ mRNA levels. However, BAL fluid IL-5 protein was increased. There was an accompanying increase in lung regulatory T cells assessed by flow cytometry. Responses to triple challenge with ovalbumin were much less affected by Bif feeding, including unchanged cytokine levels, ovalbumin-specific IgE and airway hyperresponsiveness to methacholine.

CONCLUSION

These results show modest immunoregulatory effects of oral feeding with Bif with inhibition of certain components of allergen-induced airway inflammation that is associated with the expansion of regulatory T cells in the lungs but that is overcome by repeated allergen exposure.

Intravenous immunoglobulin attenuates airway inflammation through induction of forkhead box protein 3-positive regulatory T cells

BACKGROUND

Intravenous immunoglobulin (IVIG) is a frequently used disease-modifying therapy for a large spectrum of autoimmune and inflammatory conditions, yet its mechanisms of action are incompletely understood. Using a robust murine model of antigen-driven allergic airways disease, we have demonstrated that IVIG markedly improves ovalbumin (OVA)-induced airway hyperresponsiveness characterized by 4- to 6-fold enhancement in regulatory T (Treg) cells in pulmonary and associated lymphoid tissues.

OBJECTIVE

We sought to determine whether IVIG induces antigen-specific Treg cells and to address cellular interactions that lead to induction of Treg cells by IVIG.

METHODS

C57Bl/6 mice were sensitized and challenged by means of intranasal OVA exposure. IVIG or albumin control was administered 24 hours before challenge. Treg cells were tracked by using green fluorescent protein (GFP)-forkhead box protein 3 (Foxp3) knock-in reporter mice (Foxp3(GFP)), and Treg cell and dendritic cell (DC) phenotypes and activities were elucidated by using coculture and flow cytometry.

RESULTS

IVIG therapy of OVA-sensitized and OVA-challenged mice induced antigen-specific forkhead box protein 3 (Foxp3)-positive Treg cells from non-Treg cell precursors. The induced Treg cells home specifically to the lungs and draining lymph nodes and have greatly potentiated suppressive activity compared with that seen in Treg cells purified from control mice. Induction of Treg cells is mediated by tolerogenic DCs generated after IVIG exposure. Compared with albumin-treated, OVA-exposed mice, IVIG-primed DCs express altered Notch ligands, including increased Delta-4 and reduced Jagged-1 levels, reflecting decreased T(H)2 polarization. Furthermore, IVIG-primed DCs can stimulate Treg cell differentiation from uncommitted Foxp3(-)CD4(+) T cells ex vivo, and adoptive transfer of IVIG-primed DCs abrogates airway hyperresponsiveness and induces Treg cells.

CONCLUSION

The anti-inflammatory effects of IVIG therapy can be mediated by the immunomodulation of DCs, creating a bridge that induces antigen-specific, highly suppressive Treg cells.

Notch signaling in lung development and disease

Notch signaling plays an essential role in development and homeostasis of multiple organs including the lung. Dysregulation of Notch signaling has been implicated in various lung diseases including lung cancer. Here we review functions of Notch signaling in coordinating events during lung development, such as early proximodistal fate generation and branching, airway epithelial cell fate specification, alveogenesis and pulmonary vascular development. We also discuss roles of Notch in chronic obstructive pulmonary disease, progressive pulmonary fibrosis, pulmonary arterial hypertension, asthma and lung cancer.

Notch1 regulates chemotaxis and proliferation by controlling the CC-chemokine receptors 5 and 9 in T cell acute lymphoblastic leukaemia

Tumour cells often express deregulated profiles of chemokine receptors that regulate cancer cell migration and proliferation. Notch1 pathway activation is seen in T cell acute lymphoblastic leukaemia (T-ALL) due to the high frequency of Notch1 mutations affecting approximately 60% of patients, causing ligand-independent signalling and/or prolonging Notch1 half-life. We have investigated the possible regulative role of Notch1 on the expression and function of chemokine receptors CCR5, CCR9 and CXCR4 that play a role in determining blast malignant properties and localization of extramedullary infiltrations in leukaemia. We inhibited the pathway through γ-Secretase inhibitor and Notch1 RNA interference and analysed the effect on the expression and function of chemokine receptors. Our results indicate that γ-Secretase inhibitor negatively regulates the transcription level of the CC chemokine receptors 5 and 9 in T-ALL cell lines and patients' primary leukaemia cells, leaving CXCR4 expression unaltered. The Notch pathway also controls CCR5- and CCR9-mediated biological effects, ie chemotaxis and proliferation. Furthermore, engaging CCR9 through CCL25 administration rescues proliferation inhibition associated with abrogation of Notch activity. Finally, through RNA interference we demonstrated that the oncogenic isoform in T-ALL, Notch1, plays a role in controlling CCR5 and CCR9 expression and functions. These findings suggest that Notch1, acting in concert with chemokine receptors pathways, may provide leukaemia cells with proliferative advantage and specific chemotactic abilities, therefore influencing tumour cell progression and localization.

Notch signaling prevents mucous metaplasia in mouse conducting airways during postnatal development

Goblet cell metaplasia and mucus overproduction contribute to the pathogenesis of chronic lung diseases, including asthma and chronic obstructive pulmonary disease (COPD). Notch signaling regulates cell fate decisions and is crucial in controlling goblet cell differentiation in the gut epithelium. Little is known, however, about how endogenous Notch signaling influences the goblet cell differentiation program that takes place in the postnatal lung. Using a combination of genetic and in vitro approaches here we provide evidence of a novel role for Notch in restricting goblet cell differentiation in the airway epithelium during the postnatal period. Conditional inactivation of the essential Notch pathway component Pofut1 (protein O-fucosyltransferase1) in Tgfb3-Cre-expressing mice resulted in an aberrant postnatal airway phenotype characterized by marked goblet cell metaplasia, decreased Clara cell number and increase in ciliated cells. The presence of the same phenotype in mice in which the Notch transcriptional effector Rbpjk was deleted indicated the involvement of the canonical Notch pathway. Lineage study in vivo suggested that goblet cells originated from a subpopulation of Clara cells largely present in proximal airways in which Notch was disrupted. The phenotype was confirmed by a panel of goblet cell markers, showed no changes in cell proliferation or altered expression of proinflammatory cytokines and was associated with significant downregulation of the bHLH transcriptional repressor Hes5. Luciferase reporter analysis suggested that Notch directly repressed MUC5AC transcription in lung epithelial cells. The data suggested that during postnatal life Notch is required to prevent Clara cells from differentiating into goblet cells.

Intravenous immunoglobulin attenuates airway hyperresponsiveness in a murine model of allergic asthma

BACKGROUND

Intravenous immunoglobulin (IVIG) has potent anti-inflammatory and immune-modulating properties. IVIG has been utilized as a steroid-sparing agent in severe asthma, but the results of clinical trials have been conflicting.

OBJECTIVE

To determine whether IVIG is able to attenuate bronchial reactivity, pulmonary inflammation and T cell function using a murine model of allergic airways disease.

METHODS

BALB/c or C57BL/6 mice were sensitized to ovalbumin (OVA) or a phosphate-buffered saline control using local nasal sensitization, and then received five intranasal challenges on days 28-32 before sacrifice. Mice were treated intraperitoneally with either IVIG (1-2 g/kg) or equivalent human serum albumin 24 h before the first OVA challenge. Bronchial reactivity to methacholine was examined using the FlexiVent small animal ventilator. We evaluated pulmonary histology, mRNA from lung digests for T-helper type 2 (Th2)-related genes and bronchoalveolar lavage for cell counts and cytokines. Splenocytes were utilized to study OVA-induced cell proliferation, cytokine production and dendritic cell maturation.

RESULTS

IVIG markedly attenuated the perivascular and peribronchial pulmonary inflammation, and decreased bronchial hyperresponsiveness to methacholine. IVIG treatment of splenocytes from sensitized animals diminished cellular proliferation to OVA, whereas IVIG treatment in vivo markedly attenuated OVA-driven splenocyte proliferation. This is accompanied by diminished IL-13 and TNF-α levels in splenocyte culture, decreased expression of Jagged-1, increased Delta-4 and decreased GATA-3 mRNA levels, signs that IVIG has suppressed the expected Th2 response that accompanies repeated allergen exposure. Increased regulatory T cells were found in draining pulmonary lymph nodes in IVIG-treated mice but not in controls.

CONCLUSIONS AND CLINICAL RELEVANCE

IVIG was effective in ameliorating allergic airway disease in our model. IVIG may be a promising adjunct therapy requiring further study for patients with severe asthma.

IL-9 production by regulatory T cells recruits mast cells that are essential for regulatory T cell-induced immune suppression

Both mast cells (MCs) and regulatory T cells (Tregs) have gained attention as immunosuppressive cell populations. To investigate a possible interaction, we used the Th1- and Th17-dependent model of nephrotoxic serum nephritis (NTS), in which both MCs and Tregs have been shown to play a protective role. Transfer of wild-type (wt) Tregs into wt recipients almost completely prevents development of NTS and leads to a profound increase of MCs in the renal draining lymph nodes (LNs). By contrast, transfer of wt Tregs into animals deficient in MCs, which are characterized by an exaggerated susceptibility to NTS, no longer exhibited protective effects. Blocking the pleiotropic cytokine IL-9, known to be involved in MC recruitment and proliferation, by means of a mAb in mice receiving Tregs abrogated protection from NTS. Moreover, transfer of IL-9-deficient Tregs also failed to protect from NTS. In the absence of Treg-derived IL-9, MCs fail to accumulate in the LNs, despite the fact that IL-9 deficiency does not alter the general suppressive activity of Tregs. In summary, to our knowledge, we provide the first direct in vivo evidence that the nephroprotective, anti-inflammatory effects of Tregs critically depend on IL-9-mediated attraction of MCs into kidney-draining LNs.

Notch ligand delta-like 4 regulates development and pathogenesis of allergic airway responses by modulating IL-2 production and Th2 immunity

Activation of the canonical Notch pathways has been implicated in Th cell differentiation, but the role of specific Notch ligands in Th2-mediated allergic airway responses has not been completely elucidated. In this study, we show that delta-like ligand 4 (Dll4) was upregulated on dendritic cells in response to cockroach allergen. Blocking Dll4 in vivo during either the primary or secondary response enhanced allergen-induced pathogenic consequences including airway hyperresponsiveness and mucus production via increased Th2 cytokines. In vitro assays demonstrated that Dll4 regulates IL-2 in T cells from established Th2 responses as well as during primary stimulation. Notably, Dll4 blockade during the primary, but not the secondary, response increased IL-2 levels in lung and lymph node of allergic mice. The in vivo neutralization of Dll4 was associated with increased expansion and decreased apoptosis during the primary allergen sensitization. Moreover, Dll4-mediated Notch activation of T cells during primary stimulation in vitro increased apoptosis during the contraction/resting phase of the response, which could be rescued by exogenous IL-2. Consistent with the role for Dll4-mediated IL-2 regulation in overall T cell function, the frequency of IL-4-producing cells was also significantly altered by Dll4 both in vivo and in vitro. These data demonstrate a regulatory role of Dll4 both in initial Th2 differentiation and in Th2 cytokine production in established allergic responses.

Guidance molecules in lung cancer

Guidance molecules were first described in the nervous system to control axon outgrowth direction. They are also widely expressed outside the nervous system where they control cell migration, tissue development and establishment of the vascular network. In addition, they are involved in cancer development, tumor angiogenesis and metastasis. This review is primarily focused on their functions in lung cancer and their involvement in lung development is also presented. Five guidance molecule families and their corresponding receptors are described, including the semaphorins/neuropilins/plexins, ephrins and Eph receptors, netrin/DCC/UNC5, Slit/Robo and Notch/Delta. In addition, the possibility to target these molecules as a therapeutic approach in cancer is discussed.