Interleukin-10 inhibits antigen-induced cellular recruitment into the airways of sensitized mice

IL-10+ regulatory B cells mitigate atopic dermatitis by suppressing eosinophil activation

Atopic dermatitis (AD) presents significant therapeutic challenges due to its poorly understood etiology. Eosinophilia, a hallmark of allergic inflammation, is implicated in AD pathogenesis. Interleukin-10 (IL-10)-producing regulatory B (Breg) cells exhibit potent anti-inflammatory effects. However, their role in controlling AD-related eosinophilia is not well understood. To investigate the impact of eosinophils on AD, we employed IL-5Rα-deficient (Il5ra-/-) mice, which lack functional eosinophils. Induction of AD in these mice resulted in attenuated disease symptoms, underscoring the critical role of eosinophils in AD development. Additionally, the adoptive transfer of purified Breg cells into mice with AD significantly alleviated disease severity. Mechanistic studies revealed that IL-10 produced by Breg cells directly inhibits eosinophil activation and infiltration into the skin. In vitro experiments further confirmed that Breg cells inhibited eosinophil peroxidase secretion in an IL-10-dependent manner. Our collective findings demonstrate that IL-10 from Breg cells alleviates AD by suppressing eosinophil activation and tissue infiltration. This study elucidates a novel regulatory mechanism of Breg cells, providing a foundation for future Breg-mediated therapeutic strategies for AD.

Endogenous inhibitory mechanisms in asthma

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

Interleukin-10-alveolar macrophage cell membrane-coated nanoparticles alleviate airway inflammation and regulate Th17/regulatory T cell balance in a mouse model

Background

Allergic airway disease (AAD) is a chronic disease characterized by airway inflammation, bronchoconstriction, and hyperresponsiveness. Although exogenous interleukin-10 (IL-10) alleviates allergic inflammation, it has a short half-life in vivo. Cell membrane-coated nanomaterials have been shown to protect therapeutic payloads and increase therapeutic efficacy.

Objective

This study was aimed at investigating the efficacy of a novel macrophage-based nanoparticle drug for the treatment of house dust mite (HDM)-induced allergic airway diseases.

Methods

IL-10-poly (lactic-co-glycolic acid (PLGA) nanoparticles were encapsulated in alveolar macrophage cell membranes. An allergic airway disease mouse model was established by repeated inhalation of HDM extracts. The mice were treated with free IL-10, IL-10-PLGA nanoparticles (IL10-NP), or IL-10-alveolar macrophage cell membrane-coated nanoparticles (IL10-AMNP). The therapeutic effects were evaluated by measuring airway hyperresponsiveness, lung inflammation, cytokine levels, and regulatory T cells (Treg)- T-helper 17 (Th17) cell balance.

Results

Compared to free IL-10, IL10-AMNP significantly reduced airway hyperresponsiveness and T-helper 2 (Th2)/Th17 cytokines and inhibited neutrophilia and eosinophilia recruitment into the airways of HDM-induced mouse models. Additionally, the balance between Tregs and Th17 cells was significantly improved in groups treated with IL10-AMNP.

Conclusion

This study demonstrated that PLGA nanoparticle cores coated with alveolar macrophage cell membranes can effectively deliver therapeutic cytokines to the lungs and improve the homeostatic balance between Tregs and Th17 cells. These findings suggest that macrophage-based nanoparticle drugs represent a promising approach for treating allergic airway diseases.

Study on the Mechanism of Allergic Rhinitis Based on the Expression of FIB, PCT, hs-CRP, and Th17/Treg-IL10/IL-17 Axis Balance

BACKGROUND

The pathogenesis of allergic rhinitis (AR) is ambiguous, while it is clear that various immune cells and cytokines play crucial roles in its occurrence and development.

AIM

To investigate the effect of exogenous interleukin-10 (IL-10) on the expression of fibrinogen (FIB), procalcitonin (PCT), hypersensitive C-reactive protein (hs-CRP), and Th17/Treg-IL10/IL-17 axis balance in the nasal mucosa of rats with AR.

METHOD

In this study, 48 female-specific pathogen-free Sprague-Dawley rats were randomly divided into 3 groups: blank control group, AR group, and IL-10 intervention group. The AR model was established in the AR group and IL-10 group. The rats in the control group were treated with normal saline; the rats in the AR group were given 20 μL of saline containing 50 μg of ovalbumin (OVA) every day. The rats in the IL-10 intervention group were intraperitoneally injected with 1 mL of 40 pg/kg IL-10 and provided with OVA. The IL-10 intervention group was composed of mice with AR that received IL-10. The behavior of nasal allergic symptoms (such as nasal itching, sneezing, and runny nose) and the hematoxylin and eosin staining of nasal mucosa were observed. The levels of FIB, PCT, hs-CRP, IgE, and OVA sIgE in serum were determined by enzyme-linked immunosorbent assay. The levels of Treg and Th17 cells in serum were detected by flow cytometry. The protein levels of TGF-β, IL-10, and IL-17 in nasal mucosa were detected by the Western-blot method.

RESULTS

The scores of snots, nasal itching, and sneezing in the AR group were significantly higher than those in the control group, while the scores of the above symptoms in the IL-10 intervention group were lower than those in the AR group. The levels of FIB, PCT, hs-CRP, IgE, and OVA sIgE in serum and the protein levels of IL-10 and IL-17 in the nasal mucosa in the AR group were higher than those in the blank control group. Meanwhile, the levels of FIB, PCT, hs-CRP, IgE, and OVA sIgE in serum and IL-10 and IL-17 protein in the nasal mucosa in the IL-10 group were lower than those in the AR group.

CONCLUSION

IL-10 can relieve the allergy of AR rats by affecting the expression of FIB, PCT, and hs-CRP, as well as the balance of the Th17/Treg-IL10/IL-17 axis in the nasal mucosa of AR rats.

Allergen immunotherapy, cancer, and immune disorders

PURPOSE OF REVIEW

The purpose of this review is to provide an update on the intriguing relationships between allergies, allergen immunotherapy, cancer, and immune disorders. Allergic diseases and cancer are increasing in incidence and prevalence and a potential relationship, or not, between these diseases have been suggested for many years.

RECENT FINDINGS

Recent findings suggest that there may be some causative effects between certain types of cancer and allergic diseases, as described in the text. Some types of cancer may be more linked to the presence of an allergic disease, than others. However, epigenetic factors, such as tobacco smoke alcohol and toxic substances should also be taken into consideration.

SUMMARY

The association between allergy and cancer is complex and depends on the specific allergy and the specific organ under consideration. Regarding pancreatic cancer, colorectal cancer (CRC), and glioma, all types of allergies were shown to be a protective factor. Conversely, asthma is a risk factor for lung cancer as is atopic dermatitis for skin cancer. Despite extensive research, no definite relationship has been determined, and no clear relationship, either positive or negative, to allergies can be observed. These results should be corroborated with large epidemiological well designed prospective studies due to some weaknesses in the previous investigations.

Regulated on Activation, Normal T cell Expressed and Secreted (RANTES) drives the resolution of allergic asthma

RANTES is implicated in allergic asthma and in T cell-dependent clearance of infection. RANTES receptor family comprises CCR1, CCR3, and CCR5, which are G-protein-coupled receptors consisting of seven transmembrane helices. Infections with respiratory viruses like Rhinovirus cause induction of RANTES production by epithelial cells. Here, we studied the role of RANTES in the peripheral blood mononuclear cells in cohorts of children with and without asthma and validated and extended this study to the airways of adults with and without asthma. We further translated these studies to a murine model of asthma induced by house dust mite allergen in wild-type RANTES and CCR5-deficient mice. Here we show an unpredicted therapeutic role of RANTES in the resolution of allergen-induced asthma by orchestrating the transition of effector GATA-3+CD4+ T cells into immune-regulatory-type T cells and inflammatory eosinophils into resident eosinophils as well as increased IL-10 production in the lung.

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RANTES is associated with allergic asthma and T cell-dependent clearance of infections

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RANTES is upregulated in asthmatic airways reflecting ongoing airway cell activation

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Rhinovirus inhibited and antiviral agonist induced RANTES in PBMCs from asthmatics

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Experimental treatment with RANTES (rRANTES) in the airways reduced local eosinophils

CpG-ODN Signaling via Dendritic Cells-Expressing MyD88, but Not IL-10, Inhibits Allergic Sensitization

Allergen-specific T helper (Th)2 cells orchestrate upon allergen challenge the development of allergic eosinophilic lung inflammation. Sensitization with alum adjuvant, a type 2 adjuvant, has been used extensively in animal models of allergic lung disease. In contrast, type 1 adjuvants like CpG-ODN, a synthetic toll-like receptor 9 agonist, inhibit the development of Th2 immunity. CpG-ODN induce type 1 and suppressive cytokines that influence Th2 cell differentiation. Here, we investigated the immune modulatory effect of CpG-ODN on allergic sensitization to OVA with alum focusing on dendritic cells (DCs) expressing the MyD88 molecule and the suppressive IL-10 cytokine. Using mice with specific cell deletion of MyD88 molecule, we showed that CpG-ODN suppressed allergic sensitization and consequent lung allergic inflammation signaling through the MyD88 pathway on dendritic cells, but not on B-cells. This inhibition was associated with an increased production of IL-10 in the bronchoalveolar lavage fluid. Sensitization to OVA with CpG-ODN of IL-10-deficient, but not wild-type mice, induced a shift towards Th1 pattern of inflammation. Employing bone marrow-derived dendritic cells (BM-DCs) pulsed with OVA for sensitizations with or without CpG-ODN, we showed that IL-10 is dispensable for the inhibition of allergic lung Th2 responses by CpG-ODN. Moreover, the lack of IL-10 on DCs was not sufficient for the CpG-ODN-induced immune-deviation towards a Th1 pattern. Accordingly, we confirmed directly the role of MyD88 pathway on DCs in the inhibition of allergic sensitization.

Relationship between various cytokines implicated in asthma

Asthma is a complex disorder involving immunologic, environmental, genetic and other factors. Today, asthma is the most common disease encountered in clinical medicine in both children and adults worldwide. Asthma is characterized by increased responsiveness of the tracheobronchial tree resulting in chronic swelling and inflammation of the airways recognized to be controlled by the T-helper 2 (Th2) lymphocytes, which secrete cytokines to increase the production of IgE by B cells. There are many cytokines implicated in the development of the chronic inflammatory processes that are often observed in asthma. Ultimately, these cytokines cause the release of mediators such as histamine and leukotrienes (LT), which in turn promote airway remodeling, bronchial hyperresponsiveness and bronchoconstriction. The CD4⁺ T-lymphocytes from the airways of asthmatics express a panel of cytokines that represent the Th2 cells. The knowledge derived from numerous experimental and clinical studies have allowed physicians and scientists to understand the normal functions of these cytokines and their roles in the pathogenesis of asthma. The main focus of this review is to accentuate the relationship between various cytokines implicated in human asthma. However, some key findings from animal models will be highlighted to support the discoveries from clinical studies.

Anti-inflammatory potential of pyocyanin in LPS-stimulated murine macrophages

Context: Pyocyanin is a typical Pseudomonas aeruginosa virulence factor, a common Gram-negative rod responsible for a wide range of severe nosocomial infections. There is evidence indicating that pyocyanin has multiple biological activities, but little is known about anti-inflammatory properties. Objective: This study investigated pyocyanin effect on nitric oxide and cytokine production in lipopolysaccharide (LPS)-activated murine peritoneal macrophages. Materials and methods: Macrophages were incubated in the presence and absence of pyocyanin (1, 5, 10, 50, and 100 µM) with and without LPS (1 µg/mL). Nitric oxide production was determined by Griess reagent and tumor necrosis factor (TNF)-α and interleukin (IL)-1β production was assessed by enzyme-linked immunosorbent assay. In addition, pyocyanin effects on zymosan A-induced peritonitis in mice were evaluated. Results: Pyocyanin (5 and 10 µM) decreased nitric oxide, TNF-α, and IL-1β production independent of macrophage death. On the other hand, in vivo, pyocyanin (5 mg/kg) was not able to affect leukocyte migration into the site of inflammation. Discussion and conclusion: Thus, our findings suggest that pyocyanin exerts anti-inflammatory effects on murine peritoneal macrophages, downregulating nitric oxide, TNF-α, and IL-1β levels, which seems to be independent of cell migration. These effects may represent a mechanism of immune evasion; nevertheless more detailed studies should be performed to confirm this hypothesis.

Genetic susceptibility to severe asthma with fungal sensitization

Severe asthma is problematic and its pathogenesis poorly understood. Fungal sensitization is common, and many patients with severe asthma with fungal sensitization (SAFS), used to denote this subgroup of asthma, respond to antifungal therapy. We have investigated 325 haplotype-tagging SNPs in 22 candidate genes previously associated with aspergillosis in patients with SAFS, with comparisons in atopic asthmatics and healthy control patients, of whom 47 SAFS, 279 healthy and 152 atopic asthmatic subjects were genotyped successfully. Significant associations with SAFS compared with atopic asthma included Toll-like receptor 3 (TLR3) (p = .009), TLR9 (p = .025), C-type lectin domain family seven member A (dectin-1) (p = .043), interleukin-10 (IL-10) (p = .0010), mannose-binding lectin (MBL2) (p = .007), CC-chemokine ligand 2 (CCL2) (2 SNPs, p = .025 and .041), CCL17 (p = .002), plasminogen (p = .049) and adenosine A2a receptor (p = .024). These associations differ from those found in ABPA in asthma, indicative of contrasting disease processes. Additional and broader genetic association studies in SAFS, combined with experimental work, are likely to contribute to our understanding of different phenotypes of problematic asthma.

Differential gene network analysis for the identification of asthma-associated therapeutic targets in allergen-specific T-helper memory responses

BACKGROUND

Asthma is strongly associated with allergic sensitization, but the mechanisms that determine why only a subset of atopics develop asthma are not well understood. The aim of this study was to test the hypothesis that variations in allergen-driven CD4 T cell responses are associated with susceptibility to expression of asthma symptoms.

METHODS

The study population consisted of house dust mite (HDM) sensitized atopics with current asthma (n = 22), HDM-sensitized atopics without current asthma (n = 26), and HDM-nonsensitized controls (n = 24). Peripheral blood mononuclear cells from these groups were cultured in the presence or absence of HDM extract for 24 h. CD4 T cells were then isolated by immunomagnetic separation, and gene expression patterns were profiled on microarrays.

RESULTS

Differential network analysis of HDM-induced CD4 T cell responses in sensitized atopics with or without asthma unveiled a cohort of asthma-associated genes that escaped detection by more conventional data analysis techniques. These asthma-associated genes were enriched for targets of STAT6 signaling, and they were nested within a larger coexpression module comprising 406 genes. Upstream regulator analysis suggested that this module was driven primarily by IL-2, IL-4, and TNF signaling; reconstruction of the wiring diagram of the module revealed a series of hub genes involved in inflammation (IL-1B, NFkB, STAT1, STAT3), apoptosis (BCL2, MYC), and regulatory T cells (IL-2Ra, FoxP3). Finally, we identified several negative regulators of asthmatic CD4 T cell responses to allergens (e.g. IL-10, type I interferons, microRNAs, drugs, metabolites), and these represent logical candidates for therapeutic intervention.

CONCLUSION

Differential network analysis of allergen-induced CD4 T cell responses can unmask covert disease-associated genes and pin point novel therapeutic targets.

T helper subsets in allergic eye disease

PURPOSE OF REVIEW

Ocular allergy is an IgE-mediated disease that results in inflammation of the conjunctiva and, in more severe cases, the cornea. This is driven by an immediate hypersensitivity response via mast cells, followed by a late phase response mediated by eosinophils both of which are indeed dependent on T helper (Th) lymphocyte activity. Here, we provide an update on Th subsets [Th1, Th2, Th17, and T regulatory (Treg)] and their relevance in ocular allergy.

RECENT FINDINGS

Recent evidence in ocular allergy points to an involvement of other Th subsets, in addition to Th2. However, how these subsets are activated and their role in mediating the different clinical forms is poorly understood. Novel mouse models may facilitate addressing such unknowns, and future challenges will involve how to translate such findings into more effective and 'patho-specific' treatments.

SUMMARY

Ocular allergy, especially in severe forms, involves subsets other than Th2. Th1 cells have been detected in mild and severe forms, and recent evidence points to a possible role for IL-17 in severe disease. Tregs, on the other hand, dampen pathogenic Th cell function and allergy immunotherapy is associated with Treg augmentation in disease management. Further understanding of Th biology is warranted and may lead to better therapies.

Enhanced inflammation in aged mice following infection with Streptococcus pneumoniae is associated with decreased IL-10 and augmented chemokine production

Streptococcus pneumoniae is the most common cause of severe pneumonia in the elderly. However, the impact of aging on the innate inflammatory response to pneumococci is poorly defined. We compared the innate immune response in old vs. young adult mice following infection with S. pneumoniae. The accumulation of neutrophils recovered from bronchoalveolar lavage fluid and lung homogenates was increased in aged compared with young adult mice, although bacterial outgrowth was similar in both age groups, as were markers of microvascular leak. Aged mice had similar levels of IL-1β, TNF, IFN-γ, IL-17, and granulocyte colony-stimulating factor following S. pneumoniae infection, compared with young mice, but increased levels of the chemokines CXCL9, CXCL12, CCL3, CCL4, CCL5, CCL11, and CCL17. Moreover, levels of IL-10 were significantly lower in aged animals. Neutralization of IL-10 in infected young mice was associated with increased neutrophil recruitment but no decrease in bacterial outgrowth. Furthermore, IL-10 neutralization resulted in increased levels of CCL3, CCL5, and CXCL10. We conclude that aging is associated with enhanced inflammatory responses following S. pneumoniae infection as a result of a compromised immunomodulatory cytokine response.

Interleukin-10 modulates pulmonary neutrophilic inflammation induced by cigarette smoke exposure

AIM OF THE STUDY

Interleukin (IL)-10 is an anti-inflammatory cytokine, but its role in cigarette smoke (CS)-induced inflammation and chronic obstructive pulmonary disease (COPD) has not been fully elucidated. The purpose of this study was to investigate the effect of IL-10 deficiency on CS-induced pulmonary inflammation in mice in vivo and in vitro.

MATERIALS AND METHODS

IL-10-deficient and wild-type control mice with a C57BL6/J genetic background were exposed to CS, and inflammatory cells in bronchoalveolar lavage fluid (BALF) and mRNA of cytokines in lung were evaluated with enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

During 12 days of daily CS exposure to wild-type mice, neutrophil counts in BAL fluid and tumor necrosis factor (TNF)-α mRNA expression were increased, peaked at day 8, and then declined on day 12 when the level of IL-10 reached its peak. In IL-10-deficient mice, neutrophil recruitment and TNF-α mRNA levels induced by CS exposure were significantly greater than those in wild-type mice. Keratinocyte-derived chemokine (KC; murine ortholog of human CXCL8) and granulocyte macrophage colony-stimulating factor (GM-CSF) mRNA levels or matrix metalloproteinase(MMP)-9 protein levels were not correlated with neutrophil count.

CONCLUSIONS

IL-10 had a modulatory effect on CS-induced pulmonary neutrophilic inflammation and TNF-α expression in mice in vivo and therefore appears to be an important endogenous suppressor of airway neutrophilic inflammation.

A human monoclonal anti-TNF alpha antibody (adalimumab) reduces airway inflammation and ameliorates lung histology in a murine model of acute asthma

BACKGROUND

A few experimental studies related to asthma have unveiled the beneficial effects of TNF alpha blocking agents on the airway histology, cytokine levels in bronchoalveolar lavage and bronchial hyper-responsiveness. In the current study, we aimed to assess the effect of adalimumab on the inflammation and histology of asthma in a murine model.

METHOD

Twelve-week-old BALB/c (H-2d/d) female rats (n=18) were allocated into three groups, including (group I) control (phosphate-buffered saline was implemented), (group II) asthma induced with OVA (n=6), and (group III) asthma induced with OVA+treated with adalimumab (n=6). Rats were executed on the 28th day of the study. The lung samples were fixed in 10% neutral buffered formalin. Lung parenchyma, alveolus, peribronchial and perivascular inflammation were assessed. Lung pathological scoring was performed.

RESULT

Severity of lung damage was found to be reduced significantly in the asthma induced with OVA+treated with adalimumab group. When compared with the untreated group, adalimumab significantly reduced the inflammatory cells around the bronchi and bronchioles, and reduced inflammation of the alveolar wall and alveolar wall thickness as well (median score=1, p=0.52). Peribronchial smooth muscle hypertrophy and oedema were significantly reduced after adalimumab administration.

CONCLUSION

Adalimumab (a human monoclonal anti-TNF alpha antibody) therapy significantly reduced the severity of lung damage by decreasing cellular infiltration and improvement on the lung histology in a murine model of acute asthma.

The role of macrophage IL-10/innate IFN interplay during virus-induced asthma

Activation through different signaling pathways results in two functionally different types of macrophages, the pro-inflammatory (M1) and the anti-inflammatory (M2). The polarization of macrophages toward the pro-inflammatory M1 phenotype is considered to be critical for efficient antiviral immune responses in the lung. Among the various cell types that are present in the asthmatic airways, macrophages have emerged as significant participants in disease pathogenesis, because of their activation during both the inflammatory and resolution phases, with an impact on disease progression. Polarized M1 and M2 macrophages are able to reversibly undergo functional redifferentiation into anti-inflammatory or pro-inflammatory macrophages, respectively, and therefore, macrophages mediate both processes. Recent studies have indicated a predominance of M2 macrophages in asthmatic airways. During a virus infection, it is likely that M2 macrophages would secrete higher amounts of the suppressor cytokine IL-10, and less innate IFNs. However, the interactions between IL-10 and innate IFNs during virus-induced exacerbations of asthma have not been well studied. The possible role of IL-10 as a therapy in allergic asthma has already been suggested, but the divergent roles of this suppressor molecule in the antiviral immune response raise concerns. This review attempts to shed light on macrophage IL-10-IFNs interactions and discusses the role of IL-10 in virus-induced asthma exacerbations. Whereas IL-10 is important in terminating pro-inflammatory and antiviral immune responses, the presence of this immune regulatory cytokine at the beginning of virus infection could impair the response to viruses and play a role in virus-induced asthma exacerbations.

Exogenous interleukin-10 alleviates allergic inflammation but inhibits local interleukin-10 expression in a mouse allergic rhinitis model

Background

Interleukin-10 (IL-10) has an important anti-inflammatory and immunoregulatory function, and its expression is negatively correlated with the development and severity of allergic rhinitis (AR). However, the in vivo effects of exogenous IL-10 on AR have not been studied and the mechanisms underlying the effects of IL-10 have not been fully understood. Here, we investigated the effects of intranasal administration of recombinant mouse (rm) IL-10 on the expression of Th responses and local IL-10 in a mouse model of AR induced by ovalbumin.

Results

Administration of rmIL-10 during challenge significantly reduced the number of eosinophils and mast cells, as well as Type 2 helper T (Th2) and Th17 cell related cytokine and transcription factor levels in the nasal mucosa and nasal lavage fluid in AR mice. The rmIL-10 treatment significantly inhibited the number of IL-10-positive cells and IL-10 mRNA expression in the nasal mucosa in AR mice.

Conclusion

Our results show that exogenous IL-10 administrated in challenge phase alleviates nasal allergic inflammation in AR mice, most likely by inhibiting Th2 and Th17 responses. It can also inhibit local IL-10 levels in the nasal mucosa. Our findings indicate that IL-10 may have the potential as an inhibitor of AR.

The cell-to-cell coordination between activated T cells and CpG-stimulated macrophages synergistically induce elevated levels of IL-10 via NF-κB1, STAT3, and CD40/CD154

Background

Studies into the regulation of interleukin-10 (IL-10), have focused only on the molecular or single-cell level. The cues that induce IL-10 in the context of cell-to-cell communication are scarce. To fill this gap, this study elucidates the cell-to-cell interaction dependent regulation of IL-10.

Results

The simultaneous activation of CD4⁺ T cells via CD3/CD28 and stimulation of macrophages via CpG and their intercellular communication with each other in the same microenvironment is necessary to induce a synergistic expression of IL-10. NF-κB1, ERK, and STAT3 are positive regulators of this cell-to-cell communication mediated molecular change of IL-10 induction. Strikingly, the activation of CD40/CD154 signaling is a negative regulator of IL-10 levels by CD3/CD28/CpG.

Conclusions

These findings are of prominence as CD3/CD28/CpG treatment can induce the anti-inflammatory cytokines IL-10 and IL-30, and the activation or inhibition of the CD40/CD154 acts as molecular rheostat of the expression of IL-10 or IL-30. More importantly, this not only serves as an example of IL-10 regulation at the cellular via coordination of two signals from two cell types, but these findings also lay the molecular and cellular groundwork for future studies to investigate how to manipulate IL-10 or IL-30 production during inflammation, cancer, or autoimmune diseases.

Dual role of interleukin-10 in the regulation of respiratory syncitial virus (RSV)-induced lung inflammation

RSV lower respiratory tract infections (LRTI) are among the most common diseases necessitating hospital admission in children. In addition to causing acute respiratory failure, RSV infections are associated with sequelae such as secondary bacterial infections and reactive airway disease. One characteristic host response observed in severe RSV-induced LRTI and/or subsequent development of asthma is increased expression of interleukin (IL)-10. However, contradictory results have been reported regarding whether IL-10 inhibits asthmatic responses or intensifies the disease. We aimed to reconcile these discordant observations by elucidating the role of IL-10 in regulating the host response to RSV LRTI. In this study, we used a lung-specific, inducible IL-10 over-expression (OE) transgenic mouse model to address this question. Our results showed that the presence of IL-10 at the time of RSV infection not only attenuated acute inflammatory process (i.e. 24 h post-infection), but also late inflammatory changes [characterized by T helper type 2 (Th2) cytokine and chemokine expression]. While this result appears contradictory to some clinical observations where elevated IL-10 levels are observed in asthmatic patients, we also found that delaying IL-10 OE until the late immune response to RSV infection, additive effects rather than inhibitory effects were observed. Importantly, in non-infected, IL-10 OE mice, IL-10 OE alone induced up-regulation of Th2 cytokine (IL-13 and IL-5) and Th2-related chemokine [monocyte chemoattractant protein 1 (MCP-1), chemokine (C-C motif) ligand 3 (CCL3) and regulated upon activation normal T cell expressed and secreted (RANTES)] expression. We identified a subset of CD11b(+)CD11c(+)CD49b(+)F4/80(-)Gr-1(-) myeloid cells as a prinicipal source of IL-10-induced IL-13 production. Therefore, the augmented pathological responses observed in our 'delayed' IL-10 over-expression model could be attributed to IL-10 OE alone. Taken together, our study indicated dual roles of IL-10 on RSV-induced lung inflammation which appear to depend upon the timing of when elevated IL-10 is expressed in the lung.

Elevated macrophage inflammatory protein 1α and interleukin-17 production in an experimental asthma model infected with respiratory syncytial virus

BACKGROUND

Respiratory syncytial virus (RSV) infection is associated with both the development and exacerbation of bronchial asthma. We examined eosinophil infiltration and the cytokine profiles of both airway and peripheral blood in antigen-sensitized mice infected with RSV to investigate the pathogenesis of exacerbations of asthma due to RSV infection.

METHODS

Ovalbumin (OVA)-sensitized mice were challenged by OVA inhalation 3 times and then infected with RSV [10(5) TCID50 (50% of tissue culture infectious dose)/25 g body weight] or mock infection immediately after the last challenge. Animals from each group, namely, the control (PBS instead of OVA inhalation plus mock infection), RSV (PBS plus RSV), OVA (OVA plus mock) and OVA/RSV (OVA plus RSV) were analyzed. Analysis included evaluation of airway responsiveness to methacholine, pathological findings in the airway by hematoxylin and eosin (HE) and Luna staining, bronchoalveolar fluid (BALF) and peripheral leukocytes counts, and concentrations of multiple cytokines/chemokines in both BALF and serum.

RESULTS

Airway responsiveness was significantly enhanced in the OVA and OVA/RSV groups compared with the control group. Levels of tissue and BALF eosinophils were higher in the OVA and OVA/RSV groups than in the RSV or control group. Significantly higher levels of macrophage inflammatory protein (MIP)-1α in BALF were observed in the OVA/RSV group compared with the 3 other groups. Production of serum IL-17 was also significantly elevated in the OVA/RSV group compared with the control or OVA group.

CONCLUSIONS

These findings suggest that MIP-1α and IL-17 may play important roles in acute exacerbation of asthma induced by RSV in an animal model.

Absence of Foxp3+ regulatory T cells during allergen provocation does not exacerbate murine allergic airway inflammation

Regulatory T cells (Tregs) play a non-redundant role in maintenance of immune homeostasis. This is achieved by suppressing both, priming of naïve cells and effector cell functions. Although Tregs have been implicated in modulating allergic immune responses, their influence on distinct phases of development of allergies remains unclear. In this study, by using bacterial artificial chromosome (BAC)-transgenic Foxp3-DTR (DEREG) mice we demonstrate that the absence of Foxp3⁺ Tregs during the allergen challenge surprisingly does not exacerbate allergic airway inflammation in BALB/c mice. As genetic disposition due to strain specificity may contribute significantly to development of allergies, we performed similar experiment in C57BL/6 mice, which are less susceptible to allergy in the model of sensitization used in this study. We report that the genetic background does not influence the consequence of this depletion regimen. These results signify the temporal regulation exerted by Foxp3⁺ Tregs in limiting allergic airway inflammation and may influence their application as potential therapeutics.

Regulatory T cells and the control of the allergic response

The study of immune regulation and tolerance has been traditionally associated with self/nonself-discrimination. However, the finding that dominant tolerance, a model that puts in evidence the active role of regulatory T cells, can develop to nonself-antigens suggests that the imposition of tolerance can be context dependent. This paper reviews the emerging field of acquired immune tolerance to non-self antigens, with an emphasis on the different subsets of induced regulatory T cells that appear to specialize in specific functional niches. Such regulatory mechanisms are important in preventing the onset of allergic diseases in healthy individuals. In addition, it may be possible to take advantage of these immune regulatory mechanisms for the induction of tolerance in cases where pathological immune responses are generated to allergens occurring in nature, but also to other immunogens such as biological drugs developed for medical therapies.

Interleukin-10 promoter polymorphisms and asthma risk: a meta-analysis

Several studies assessed the associations of interleukin-10 (IL-10) polymorphisms with asthma in different populations. However, the results were inconclusive. The aim of the present study was to further assess the associations by the method of meta-analysis. Pubmed, EMBASE, Wanfang Database, China National Knowledge Infrastructure (CNKI) and Weipu Database were searched. Data were extracted independently by two authors. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of associations. Seventeen potentially eligible articles were identified (4478 cases and 4803 controls). Significant associations between -1082A/G and -592A/C polymorphisms and asthma were observed. However, there was no significant association between -819T/C polymorphism and asthma risk. In addition, there were significant associations of the IL-10 haplotypes with asthma. In summary, this meta-analysis suggested that IL-10 promoter polymorphisms were associated with asthma risk.

Cellular and molecular mechanisms of TSLP function in human allergic disorders--TSLP programs the "Th2 code" in dendritic cells

Thymic stromal lymphopoietin (TSLP) has been recently implicated as a key molecule for initiating allergic inflammation at the epithelial cell-dendritic cell (DC) interface. In humans, aberrant TSLP expression is observed in allergic tissues, such as lesional skins of atopic dermatitis, lungs of asthmatics, nasal mucosa of atopic rhinitis and nasal polyps, and ocular surface of allergic keratoconjunctivitis. TSLP is produced predominantly by damaged epithelial cells and stimulates myeloid DCs (mDCs). TSLP-activated mDCs can promote the differentiation of naïve CD4(+) T cells into a Th2 phenotype and the expansion of CD4(+) Th2 memory cells in a unique manner dependent on OX40L, one of the tumor necrosis factor superfamily members with Th2-promoting function, and lack of production of IL-12. From a genetic point of view, multiple genome-wide association studies have repeatedly identified the TSLP gene as one of the loci associated with susceptibility to allergic diseases. Thus, TSLP is a rational therapeutic target for the treatment of allergic disorders. Elucidating the mechanisms that regulate TSLP expression and the effects of TSLP on orchestrating the immune response toward a Th2 phenotype is essential for developing anti-TSLP therapy.

Immunological approaches for tolerance induction in allergy

Allergy is the consequence of an inappropriate inflammatory immune response generated against harmless environmental antigens. In allergic disorders such as asthma and rhinitis, the Th2 mediated phenotype is a result of loss of peripheral tolerance mechanisms. In cases such as these, approaches such as immunotherapy attempt to treat the underlying cause of allergic disease by restoring tolerance. Immunotherapy initiates many complex mechanisms within the immune system that result in initiation of innate immunity, activation of both cellular and humoral B cell immunity, as well as triggering T regulatory subsets which are major players in the establishment of peripheral tolerance. Though studies clearly demonstrate immunotherapy to be efficacious, research to improve this treatment is ongoing. Investigation of allergenicity versus immunogenicity, native versus modified allergens, and the use of adjuvant and modality of dosing are all current strategies for immunotherapy advancement that will be reviewed in this article.

Inhibition of IL-10 production by maternal antibodies against Group B Streptococcus GAPDH confers immunity to offspring by favoring neutrophil recruitment

Group B Streptococcus (GBS) is the leading cause of neonatal pneumonia, septicemia, and meningitis. We have previously shown that in adult mice GBS glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is an extracellular virulence factor that induces production of the immunosuppressive cytokine interleukin-10 (IL-10) by the host early upon bacterial infection. Here, we investigate whether immunity to neonatal GBS infection could be achieved through maternal vaccination against bacterial GAPDH. Female BALB/c mice were immunized with rGAPDH and the progeny was infected with a lethal inoculum of GBS strains. Neonatal mice born from mothers immunized with rGAPDH were protected against infection with GBS strains, including the ST-17 highly virulent clone. A similar protective effect was observed in newborns passively immunized with anti-rGAPDH IgG antibodies, or F(ab')₂ fragments, indicating that protection achieved with rGAPDH vaccination is independent of opsonophagocytic killing of bacteria. Protection against lethal GBS infection through rGAPDH maternal vaccination was due to neutralization of IL-10 production soon after infection. Consequently, IL-10 deficient (IL-10^−/−) mice pups were as resistant to GBS infection as pups born from vaccinated mothers. We observed that protection was correlated with increased neutrophil trafficking to infected organs. Thus, anti-rGAPDH or anti-IL-10R treatment of mice pups before GBS infection resulted in increased neutrophil numbers and lower bacterial load in infected organs, as compared to newborn mice treated with the respective control antibodies. We showed that mothers immunized with rGAPDH produce neutralizing antibodies that are sufficient to decrease IL-10 production and induce neutrophil recruitment into infected tissues in newborn mice. These results uncover a novel mechanism for GBS virulence in a neonatal host that could be neutralized by vaccination or immunotherapy. As GBS GAPDH is a structurally conserved enzyme that is metabolically essential for bacterial growth in media containing glucose as the sole carbon source (i.e., the blood), this protein constitutes a powerful candidate for the development of a human vaccine against this pathogen.

Streptococcus agalactiae (Group B streptococcus, GBS) is the leading infectious cause of morbidity and mortality among neonates. However, there is still no satisfactory explanation of why neonates are so susceptible to GBS infections. Intrapartum antibiotic prophylaxis (IAP) was implemented in many countries but led to the emergence of antibiotic-resistant GBS strains. Therefore, maternal vaccination represents an attractive alternative to IAP. Here, we show that the high susceptibility of newborn mice to GBS infections is associated with their propensity to produce elevated amounts of immunosuppressive cytokine IL-10. We also demonstrate that IL-10 impairs neutrophil recruitment into infected organs thus preventing bacterial clearance. We identified extracellular GAPDH as the GBS factor that induces the high IL-10 production detected early upon neonatal infection. We show that maternal vaccination with recombinant GAPDH confers robust protective immunity against lethal infection with a GBS hyper-virulent strain in mice offspring. This protection can also be obtained either by antibody neutralization of GBS GAPDH or by blocking IL-10 binding to its receptor. As GBS GAPDH is an essential protein for bacterial growth, it is present in all GBS strains and thus constitutes an appropriate target antigen for a global effective vaccine against this pathogen.

An intranasal administration of Lactococcus lactis strains expressing recombinant interleukin-10 modulates acute allergic airway inflammation in a murine model

BACKGROUND

Around 300 million people world-wide suffer from asthma, and the prevalence of allergic diseases has increased. Much effort has been used in the study of mechanisms involved in the immune response observed in asthma to intervene for the treatment of this condition. During inflammation in asthma, Th2 cytokines and eosinophils are essential components of the host immune system. Furthermore, for therapeutic interventions against this disease, IL-10 is an important cytokine because it has a central role in the regulation of inflammatory cascades.

OBJECTIVE

To evaluate the immunomodulatory effect of Lactococcus lactis strains expressing recombinant IL-10 in a mouse model of ovalbumin (OVA)-induced acute airway inflammation.

METHODS

L. lactis expressing recombinant IL-10 in a cytoplasmic (LL-CYT) or secreted form (LL-SEC) and wild-type (LL-WT) were used. IL-10 production by the recombinant strains was evaluated by ELISA. After an intranasal administration of L. lactis producing recombinant IL-10 and the induction of acute allergic airway inflammation in mice, blood samples were collected to detect IgE anti-OVA, and bronchoalveolar lavage (BAL) was harvested for eosinophil count. Additionally, the lungs were collected for the detection of the eosinophil peroxidase (EPO) activity, measurement of cytokines and chemokines and evaluation of pathology.

RESULTS

Mice that received LL-CYT and LL-SEC strains showed a significant decrease in eosinophils numbers, EPO activity, anti-OVA IgE and IgG1 levels, IL-4 and CCL3 production and pulmonary inflammation and mucus hypersecretion, compared with the asthmatic group. Only the LL-CYT/OVA group showed reduced levels of IL-5, CCL2, CCL5 and CCL11.

CONCLUSION

Treatment with L. lactis producing recombinant IL-10 used in this study (LL-CYT and LL-SEC) modulated experimental airway inflammation in the mouse model independently of Treg cells. Additionally, the LL-CYT strain was more efficient in the suppression of lung inflammation.

PAS-1, an Ascaris suum protein, modulates allergic airway inflammation via CD8+γδTCR+ and CD4+CD25+FoxP3+ T cells

We have previously demonstrated that PAS-1, a 200 kDa protein from Ascaris suum, has a potent immunomodulatory effect on humoral and cell-mediated responses induced by APAS-3 (an allergenic protein from A. suum) or unrelated antigens. In this study, we investigated the mechanisms by which PAS-1 is able to induce this effect on an allergic airway inflammation induced by OVA in mice. C57BL/6 mice were adoptively transferred on day 0 with seven different PAS-1-primed cell populations: PAS-1-primed CD19(+) or B220(+) or CD3(+) or CD4(+) or CD8(+) or CD4(+) CD25⁻ or CD4(+) CD25(+) lymphocytes. These mice were immunized twice with OVA and alum by intraperitoneal route (days 0 and 7) and challenged twice by intranasal route (days 14 and 21). Two days after the last challenge, the airway inflammation was evaluated by antibody levels, cellular migration, eosinophil peroxidase levels, cytokine and eotaxin production, and pulmonary mechanical parameters. Among the adoptively transferred primed lymphocytes, only CD4(+) CD25(+) , CD8(+) or the combination of both T cells impaired the production of total IgE and OVA-specific IgE and IgG1 antibodies, eosinophilic airway inflammation, Th2-type cytokines (IL-4, IL-5 and IL-13), eotaxin release and airway hyperreactivity. Moreover, airway recruited cells from CD4(+) CD25(+) and CD8(+) T-cell recipient secreted more IL-10/TGF-β and IFN-γ, respectively. Moreover, we found that PAS-1 expands significantly the number of CD4(+) CD25(+) FoxP3(+) and CD8(+) γδTCR(+) cells. In conclusion, these findings demonstrate that the immunomodulatory effect of PAS-1 is mediated by these T-cell subsets.

Allergen-specific subcutaneous immunotherapy in allergic asthma: immunologic mechanisms and improvement

Allergic asthma is a disease characterized by persistent allergen-driven airway inflammation, remodeling, and airway hyperresponsiveness. CD4(+) T-cells, especially T-helper type 2 cells, play a critical role in orchestrating the disease process through the release of the cytokines IL-4, IL-5, and IL-13. Allergen-specific immunotherapy (SIT) is currently the only treatment with a long-term effect via modifying the natural course of allergy by interfering with the underlying immunological mechanisms. However, although SIT is effective in allergic rhinitis and insect venom allergy, in allergic asthma it seldom results in complete alleviation of the symptoms. Improvement of SIT is needed to enhance its efficacy in asthmatic patients. Herein, the immunoregulatory mechanisms underlying the beneficial effects of SIT are discussed with the ultimate aim to improve its treatment efficacy.

A novel dithiol amide CB3 attenuates allergic airway disease through negative regulation of p38 mitogen-activated protein kinase

RATIONALE

Cellular redox homeostasis altered by excessive production of reactive oxygen species (ROS) and weakening of the antioxidant defense leads to oxidative stress. Oxidative stress is characterized as a decrease in glutathione/glutathione disulfide (GSH/GSSG) and the triggering of a number of the redox-sensitive signaling cascades. Recent studies have demonstrated that ROS play an important role in the pathogenesis of airway inflammation and hyperresponsiveness.

OBJECTIVES

Here we characterized for the first time the protective properties of a new hydrophobic thiol compound, N-acetyl cysteine proline cysteine amide (CB3), in allergic airway diseases.

METHODS

We used ovalbumin (OVA)-inhaled mice to evaluate the role of CB3 as an antiinflammatory reagent and to determine its molecular signaling activity in allergic airways.

MEASUREMENTS AND MAIN RESULTS

The administration of CB3 (1-50 mg/kg) to OVA-inhaled mice restored the decreased GSH levels, enhanced IL-10 expression, and significantly reduced the increase of Th2 cytokines and OVA-specific IgE. CB3 decreased the number of inflammatory cells and airway hyperresponsiveness in the lungs. We also found that the administration of CB3 dramatically decreased the nuclear translocation of the nuclear factor-κB (NF-κB) and the phosphorylation of p38 mitogen-activated protein kinases (MAPKs) in lungs after OVA inhalation. In addition, allergen-induced airway inflammation and hyperresponsiveness were substantially reduced by the administration of inhibitors of NF-κB and p38 MAPK, BAY 11-7085, and SB 239063, respectively.

CONCLUSIONS

These results suggest that CB3 attenuates allergic airway disease by up-regulation of GSH levels as well as inhibition of NF-κB and p38 MAPK activity.

IL-10 delivery by AAV5 vector attenuates inflammation in mice with Pseudomonas pneumonia

Lung infections with Pseudomonas aeruginosa and other pathogens in cystic fibrosis (CF) cause progressive airway obstruction and tissue damage, the predominant cause of morbidity and mortality in CF. We investigated whether a recombinant adeno-associated virus type 5 (AAV5) vector expressing murine interleukin (IL)-10 (AAV5.Cbeta-mIL-10), a regulatory/anti-inflammatory cytokine, could decrease airway inflammation in IL-10 knockout mice chronically infected with mucoid P. aeruginosa. Mice that received AAV5.Cbeta-mIL10 through intratracheal inoculation produced IL-10 at an average of 25 000 pg/ml in the epithelial lining fluid (ELF) and 12 000 pg/g-lung tissue 6 weeks post-vector delivery, significantly higher levels than in placebo-treated mice. At 3 days post-infection, proinflammatory cytokines (IL-1beta, tumor necrosis factor (TNF)-alpha, macrophage inhibitory protein (MIP)-1alpha and (KC) in the ELF and lung homogenate were decreased (1-9 folds) in the AAV5.Cbeta-mIL10-treated mice accompanied by less pronounced and more localized neutrophil infiltration in lung sections, when compared with placebo-treated mice. These results suggest that AAV5.Cbeta-mIL10 induces IL-10 levels in the lungs mediating a significant anti-inflammatory response and making AAV-IL-10 gene transfer a potentially useful therapy in the treatment of CF lung disease.

Cytokine gene-modulated dendritic cells protect against allergic airway inflammation by inducing IL-10(+)IFN-gamma(+)CD4(+) T cells

Asthma is characterized by allergen-induced airway inflammation orchestrated by Th2 cells. Dendritic cells (DCs) were found to efficiently prime naive T-helper cells. Thus, modification of DC function may be used as an ideal tool to treat allergic asthma by changing CD4(+) T-cell differentiation or suppressing Th2 development. In this study, we examined whether a DC-based vaccine can be applied to DCs modified with interleukin (IL)-10- and IL-12-expressing adenoviruses to prevent ovalbumin (OVA)-induced asthma in mice. Herein, we show that these modified DCs efficiently moderated the characteristics of asthma, including expressions of OVA-specific antibodies, airway hyperresponsiveness, eosinophilic airway inflammation, and Th2 cytokines production. Additionally, IL-10 and IL-12 gene-modified DCs enhanced the development of both T-helper type 1 (Th1) and IL-10(+)IFN-gamma(+) (interferon-gamma) double-positive T cells in vivo. In vitro-generated OVA-specific IL-10(+)IFN-gamma(+)CD4(+) T cells inhibited the proliferation of naive CD4(+) T cells, and this suppressive effect was a cell contact-dependent mechanism. Furthermore, we showed that combined cytokine-modulated DCs could alleviate established allergic airway inflammation. Taken together, these results suggest that IL-10 and IL-12 gene-modulated DCs are effective in suppressing asthmatic airway inflammation through both immune deviation and immune suppression and are a potential therapeutic approach for asthma.

Synergistic therapeutic effects of combined adenovirus-mediated interleukin-10 and interleukin-12 gene therapy on airway inflammation in asthmatic mice

BACKGROUND

Asthma is a chronic disease characterized by airway inflammation caused by the dysregulated production of cytokines secreted by allergen-specific type 2 T helper (Th2) cells. Although the Th1-promoting cytokine, interleukin (IL)-12, is capable of inhibiting Th2-driven allergen-induced airway changes in mice, IL-12 also aggravates the Th1-driven inflammatory pulmonary pathology. Further, IL-10 was found to exert both anti-inflammatory and immunoregulatory activities. To avoid the side-effects of IL-12, we hypothesized that the low-dose expression of IL-10 with concomitant IL-12 administration in the airway may represent a more effective therapy for allergic airway diseases. Thus, the present study explored the immunomodulatory and therapeutic effects of IL-10 combined with IL-12 in airway inflammation in allergic asthma.

METHODS

Adenovirus-expressing murine IL-10 (Ad-IL-10) and IL-12 (Ad-IL-12) were co-administrated in an established murine model of ovalbumin (OVA)-induced asthma.

RESULTS

We found that a single combined treatment of low doses of Ad-IL-10 and Ad-IL-12 efficiently inhibited the development of airway hyper-responsiveness compared to Ad-IL-10 or Ad-IL-12 treatment alone. Moreover, both Ad-IL-10 and Ad-IL-12 treatment reduced pulmonary infiltration of eosinophils and neutrophils. In addition, histological studies showed that combined treatment was able to reduce tumor necrosis factor-alpha-mediated airway inflammation induced by IL-12 treatment. Suppression of IL-4, IL-5, Keratinocyte-derived chemokine (KC) and eotaxin in bronchoalveolar lavage fluid was also noted in OVA-immunized mice with combined Ad-IL-10 and Ad-IL-12 treatment.

CONCLUSIONS

Taken together, the results obtained in the present study indicate that co-administration of IL-12 and IL-10 may have therapeutic potential for the immunomodulatory treatment of allergic asthma.

The regulation of IL-10 production by immune cells

Interleukin-10 (IL-10), a cytokine with anti-inflammatory properties, has a central role in infection by limiting the immune response to pathogens and thereby preventing damage to the host. Recently, an increasing interest in how IL10 expression is regulated in different immune cells has revealed some of the molecular mechanisms involved at the levels of signal transduction, epigenetics, transcription factor binding and gene activation. Understanding the specific molecular events that regulate the production of IL-10 will help to answer the remaining questions that are important for the design of new strategies of immune intervention.

Pathogenic mechanisms of allergic inflammation: atopic asthma as a paradigm

Prospective studies tracking birth cohorts over periods of years indicate that the seeds for atopic asthma in adulthood are sewn during early life. The key events involve programming of functional phenotypes within the immune and respiratory systems which determine long-term responsiveness to ubiquitous environmental stimuli, particularly respiratory viruses and aeroallergens. A crucial component of asthma pathogenesis is early sensitization to aeroallergens stemming from a failure of mucosal tolerance mechanisms during the preschool years, which is associated with delayed postnatal maturation of a range of adaptive and innate immune functions. These maturational defects also increase risk for severe respiratory infections, and the combination of sensitization and infections maximizes risk for early development of the persistent asthma phenotype. Interactions between immunoinflammatory pathways stimulated by these agents also sustain the disease in later life as major triggers of asthma exacerbations. Recent studies on the nature of these interactions suggest the operation of an infection-associated lung:bone marrow axis involving upregulation of FcERlalpha on myeloid precursor populations prior to their migration to the airways, thus amplifying local inflammation via IgE-mediated recruitment of bystander atopic effector mechanisms. The key participants in the disease process are airway mucosal dendritic cells and adjacent epithelial cells, and transiting CD4(+) effector and regulatory T-cell populations, and increasingly detailed characterization of their roles at different stages of pathogenesis is opening up novel possibilities for therapeutic control of asthma. Of particular interest is the application of genomics-based approaches to drug target identification in cell populations of interest, exemplified by recent findings discussed below relating to the gene network(s) triggered by activation of Th2-memory cells from atopics.

Regulatory T cells in asthma

Asthma is characterized by T helper cell 2 (Th2) type inflammation, leading to airway hyperresponsiveness and tissue remodeling. Th2 cell-driven inflammation is likely to represent an abnormal response to harmless airborne particles. These reactions are normally suppressed by regulatory T cells, which maintain airway tolerance. The anti-inflammatory cytokine IL-10 is likely to play a central role. The role of the cytokine transforming growth factor beta (TGF-beta) is more complex, with evidence for immune suppression and remodeling in the airways. In asthmatic individuals there is a breakdown in these regulatory mechanisms. There is emerging evidence that early life events, including exposure to allergen and infections, are critical in programming effective regulatory pathways to maintain pulmonary homeostasis. In this review we examine the clinical and experimental evidence for T regulatory cell function in the lung and discuss the events that might influence the functioning of these cells. Ultimately, the ability to enhance regulatory function in affected individuals may represent an effective treatment for asthma.

TLR3 activation stimulates cytokine secretion without altering agonist-induced human small airway contraction or relaxation

Respiratory infections exacerbate chronic lung diseases promoting airway inflammation and hyperreactivity. Toll-like receptor 3 (TLR3) recognizes viral double-stranded (ds) RNA such as polyinosinic-polycytidylic acid [poly(I:C)] and stimulates innate immune responses. The objective of this study was to test the hypothesis that dsRNA promotes lung inflammation and alters airway responsiveness to cholinergic and beta-adrenergic receptor agonists in human lung slices. Human airway smooth muscle (ASM) was incubated for 24 h in poly(I:C) +/- TNFalpha and a TLR3 monoclonal antibody. Precision-cut lung slices (PCLS; 250-microm thickness) from healthy human lungs containing a small airway were incubated in 0, 10, or 100 microg/ml poly(I:C) for 24 h. Intravital microscopy of lung slices was used to quantify contractile and relaxation responsiveness to carbachol and isoproterenol, respectively. Supernatants of ASM and PCLS were analyzed for cytokine secretion using a 25-multiplex bead assay. In human ASM, poly(I:C) (0.5 microg/ml) increased macrophage inflammatory protein-1alpha (MIP-1alpha) and RANTES that was prevented by a TLR3 monoclonal receptor antibody. Incubation of human PCLS with poly(I:C) (10 and 100 microg/ml) had little effect on the log EC(50) or maximum drug effect (E(max)) for contraction and relaxation in response to carbachol and isoproterenol, respectively. The responsiveness of the same human PCLS to poly(I:C) incubation was confirmed by the robust increase in chemokines and cytokines. In separate experiments, incubation of PCLS with IL-13 or TNFalpha (100 ng/ml) increased airway sensitivity to carbachol. Poly(I:C) promotes inflammatory mediator release that was not associated with enhanced bronchoconstriction or attenuated bronchodilation in normal healthy human lung slices. Transduction at the TLR3 initiated by dsRNA stimulates downstream innate immune responses.

Regulatory T cells in bronchial asthma

The main focus of this review was the role of a specific subset of T cells with immunomodulatory or immunosuppressive activities, termed regulatory T cells (Tregs), in the pathogenesis and treatment of bronchial asthma. Evidence that these cells are important in maintaining immune homeostasis in health and exhibit impaired activity in active disease will be discussed. Their therapeutic potential is perhaps best highlighted by evidence that therapies with demonstrated efficacy in allergic and asthmatic disease are associated with the induction or restoration of regulatory T-cell function, e.g. glucocorticoids, allergen immunotherapy. Strategies to improve the safety and efficacy of these treatments and that induce or boost Tregs in bronchial asthma are discussed.

Cigarette smoke, inflammation, and lung injury: a mechanistic perspective

Inflammation is a common feature in the pathogenesis of cigarette smoke-associated diseases. The recruitment of inflammatory cells into the lung following cigarette smoke exposure presents a risk of tissue damage through the release of toxic mediators, including proteolytic enzymes and reactive oxygen species. This review represents a toxicological approach to investigation of cigarette smoke-induced lung injury, with a focus on laboratory studies and an emphasis on inflammatory mechanisms. The studies discussed in this review analyze the role of inflammation and inflammatory mediators in the development of injury. In cases where information relating to cigarette smoke is limited, examples are taken from other models of lung injury applicable to cigarette smoke. The primary aim of the review is to summarize published work so as to permit (1) an evaluation of chronic lung injury and inflammatory responses in animal models, (2) a discussion of inflammatory mediators in the development of chronic injury, and (3) identification of immunological mechanisms of injury. These studies discuss the currently understood roles of cytokines, cell adhesion molecules, and oxidative stress in inflammatory reactions and lung injury. A role for lipocortin 1 (annexin 1), a naturally occurring defense factor against inflammation, is discussed because of the possibility that impaired synthesis and degradation of lipocortin 1 will influence immune responses in animals exposed to cigarette smoke either by augmenting T helper cell Th1 response or by shifting Th1 to Th2 response. While Th1 augmentation will increase the risk for development of emphysema, Th1 to Th2 shift will favor development of asthma.

Differential potentiation of allergic lung disease in mice exposed to chemically distinct diesel samples

Numerous studies have demonstrated that diesel exhaust particles (DEP) potentiate allergic immune responses, however the chemical components associated with this effect, and the underlying mechanisms are not well understood. This study characterized the composition of three chemically distinct DEP samples (N, C, and A-DEP), and compared post-sensitization and post-challenge inflammatory allergic phenotypes in BALB/c mice. Mice were instilled intranasally with saline or 150 microg of N-DEP, A-DEP, or C-DEP with or without 20 microg of ovalbumin (OVA) on days 0 and 13, and were subsequently challenged with 20 microg of OVA on days 23, 26, and 29. Mice were necropsied 18 h post-sensitization and 18 and 48 h post-challenge. N-DEP, A-DEP, and C-DEP contained 1.5, 68.6, and 18.9% extractable organic material (EOM) and 47, 431, and 522 microg of polycyclic aromatic hydrocarbons (PAHs), respectively. The post-challenge results showed that DEP given with OVA induced a gradation of adjuvancy as follows: C-DEP approximately A-DEP > N-DEP. The C- and A-DEP/OVA exposure groups had significant increases in eosinophils, OVA-specific IgG1, and airway hyperresponsiveness. In addition, the C-DEP/OVA exposure increased the T helper 2 (T(H)2) chemoattractant chemokine, thymus and activation-regulated chemokine and exhibited the most severe perivascular inflammation in the lung, whereas A-DEP/OVA increased interleukin (IL)-5 and IL-10. In contrast, N-DEP/OVA exposure only increased OVA-specific IgG1 post-challenge. Analysis of early signaling showed that C-DEP induced a greater number of T(H)2 cytokines compared with A-DEP and N-DEP. The results suggest that potentiation of allergic immune responses by DEP is associated with PAH content rather than the total amount of EOM.

Dendritic cells genetically engineered to express IL-10 induce long-lasting antigen-specific tolerance in experimental asthma

Dendritic cells (DCs) are professional APCs that have a unique capacity to initiate primary immune responses, including tolerogenic responses. We have genetically engineered bone marrow-derived DCs to express the immunosuppressive cytokine IL-10 and tested the ability of these cells to control experimental asthma. A single intratracheal injection of OVA-pulsed IL-10-transduced DCs (OVA-IL-10-DCs) to naive mice before OVA sensitization and challenge prevented all of the cardinal features of airway allergy, namely, eosinophilic airway inflammation, airway hyperreactivity, and production of mucus, Ag-specific Igs, and IL-4. OVA-IL-10-DCs also reversed established experimental asthma and had long-lasting and Ag-specific effects. We furthermore showed, by using IL-10-deficient mice, that host IL-10 is required for mediating the immunomodulatory effects of OVA-IL-10-DCs and demonstrated a significant increase in the percentage of OVA-specific CD4(+)CD25(+)Foxp3(+)IL-10(+) regulatory T cells in the mediastinal lymph nodes of OVA-IL-10-DC-injected mice. Finally, adoptive transfer of CD4(+) mediastinal lymph node T cells from mice injected with OVA-IL-10-DCs protected OVA-sensitized recipients from airway eosinophilia upon OVA provocation. Our study describes a promising strategy to induce long-lasting Ag-specific tolerance in airway allergy.

Suppression of murine allergic airway disease by IL-2:anti-IL-2 monoclonal antibody-induced regulatory T cells

Regulatory T cells (Treg) play a decisive role in many diseases including asthma and allergen-induced lung inflammation. However, little progress has been made developing new therapeutic strategies for pulmonary disorders. In the current study we demonstrate that cytokine:antibody complexes of IL-2 and anti-IL-2 mAb reduce the severity of allergen-induced inflammation in the lung by expanding Tregs in vivo. Unlike rIL-2 or anti-IL-2 mAb treatment alone, IL-2:anti-IL-2 complexes dampened airway inflammation and eosinophilia while suppressing IL-5 and eotaxin-1 production. Mucus production, airway hyperresponsiveness to methacholine, and parenchymal tissue inflammation were also dramatically reduced following IL-2:anti-IL-2 treatment. The suppression in allergic airway disease was associated with a marked expansion of Tregs (IL-10(+)CD4(+)CD25(+) and Foxp3(+)CD4(+)CD25(+)) in the tissues, with a corresponding decrease in effector T cell responses. The ability of IL-2:anti-IL-2 complexes to suppress airway inflammation was dependent on Treg-derived IL-10, as IL-10(+/+), but not IL-10(-/-) Tregs, were capable of mediating the suppression. Furthermore, a therapeutic protocol using a model of established airway allergy highlighted the ability of IL-2:anti-IL-2 complexes to expand Tregs and prevent successive airway inflammation and airway hyperresponsiveness. This study suggests that endogenous Treg therapy may be a useful tool to combat the rising incidence of allergic airway disease.

Anti-asthmatic effect of marine red alga (Laurencia undulata) polyphenolic extracts in a murine model of asthma

The aim of the present work is focused on protective effects of an edible red alga, Laurencia undulata ethanolic (EtOH) extracts (LU) containing a large amount of polyphenols against OVA-induced murine allergic airway reactions using in vivo histological and cytokine assay. Mice sensitized and challenged with ovalbumin (OVA) showed typical asthmatic reactions as follows: an increase in the number of eosinophil in bronchoalveolar lavage fluid; a marked influx of inflammatory cells into the lung around blood vessels and airways, and airway luminal narrowing; the development of airway hyperresponsiveness; the detection of TNF-alpha and Th2 cytokines, such as IL-4 and IL-5 in the bronchoalveolar lavage (BAL) fluid; and detection of allergen-specific IgE in the serum. The successive intraperitoneal administration of LU before the last airway OVA-challenge resulted in a significant inhibition of all asthmatic reactions. These results suggest that L. undulata polyphenolic extracts possess therapeutic potential for combating bronchial asthma associated with allergic diseases.

Imidazoquinoline acts as immune adjuvant for functional alteration of thymic stromal lymphopoietin-mediated allergic T cell response

Atopic dermatitis is a major allergic disease that develops through dysregulation of Th2-mediated inflammation. Although dendritic cells (DCs) have been thought to play a critical role in the upstream phase of the allergic cascade, conventional drugs such as steroids and chemical mediator antagonists target the effector cells or factors in allergic inflammation. Recently, it has been demonstrated that interaction between thymic stromal lymphopoietin (TSLP) and human DCs plays an essential role in evoking inflammatory Th2 responses in allergy through OX40 ligand expression on DCs. In this study, we provide evidence that R848, an imidazoquinoline compound, which is a TLR ligand and a strong Th1 response-inducing reagent, is a potent adjuvant for the alteration of the Th2-inducing potency of human DCs activated by TSLP (TSLP-DCs). R848 inhibited the inflammatory Th2-inducing capacity of TSLP-DCs and redirected them to possessing an IL-10 and IFN-gamma-producing regulatory Th1-inducing capacity. This functional alteration depended on both repression of OX40 ligand expression and induction of IL-12 production from DCs by the addition of R848. Additionally, R848 had the ability to inhibit the TSLP-mediated expansion and maintenance of the Th2 memory response. These findings suggest that imidazoquinoline may be a useful in the treatment of allergic diseases that are triggered by TSLP.

Effects of repeated respiratory syncytial virus infections on pulmonary dendritic cells in a murine model of allergic asthma

BACKGROUND

Primary and secondary respiratory syncytial virus (RSV) infection differentially regulates preexisting allergic airway inflammation.

OBJECTIVES

The present study was designed to determine the effects of primary and secondary low-grade RSV infections on pulmonary dendritic cell (DC) functions.

METHODS

Eight groups of BALB/c mice were used: one group each for control primary and secondary sensitization, primary and secondary sensitization to Dermatophagoides farinae (Derf) allergen, primary and secondary infection with RSV, and primary and secondary sensitization to Derf plus infection with RSV. CD11c+ pulmonary DCs were isolated from these mice and then transferred to naïve mice followed by intranasal Derf challenge. Furthermore, either anti-IL-12 monoclonal antibody (alphaIL-12 mAb) or anti-IL-10 (alphaIL-10) mAb were injected into donor mice after Derf challenge and during RSV infection to determine the involvement of IL-12 and IL-10.

RESULTS

Primary RSV infection failed to induce polarization in DCs since it failed to induce IL-10 and IL-12 production in Derf-sensitized donor lung. In contrast, secondary RSV infection significantly enhanced IL-12 production from Derf-sensitized donor lung, thereby enhancing both Th1 and Th2 responses. During RSV infection, alphaIL-12 but not alphaIL-10 mAb treatment blocked these immunological effects.

CONCLUSION

Via IL-12, DCs may play a critical role in shifting the immune response in this experimental model of repeated respiratory viral infection in allergic asthma.

Evaluation of the anti-inflammatory effect of infliximab in a mouse model of acute asthma

BACKGROUND AND OBJECTIVE

To evaluate the potential role of anti-tumour necrosis factor (TNF)-alpha mAb (infliximab) on the inflammatory response in a mouse model of acute asthma.

METHODS

BALB/c mice received intraperitoneal (i.p.) ovalbumin (OVA) on days 0 and 14, 100 microg of OVA intranasally on day 14 and 50 microg of OVA intranasally on days 25, 26 and 27. The low-dose (2.5 mg/kg) and high-dose (6.25 mg/kg) infliximab groups received i.p. infliximab before each i.p. sensitization and on challenge days 1, 6, 13, 20 and 27. The control group received i.p. injections of normal saline with alum on days 0 and 14 and normal saline without alum on days 14, 25, 26 and 27.

RESULTS

There were statistically significant decreases in the numbers of BAL fluid (BALF) neutrophils, eosinophils, as well as lung eosinophils in both the low- and high-dose infliximab groups when compared with the control OVA sensitized/challenged group. The lower dose of infliximab did not alter lung neutrophil counts, but a marked decrease was seen with the high dose of infliximab. After treatment with low and high doses of infliximab, BALF levels of regulated on activation normal T cell expressed and secreted (RANTES), granulocyte macrophage-colony stimulating factor (GM-CSF), TNF-alpha, IL-6, macrophage inflammatory protein (MIP)-2, and levels of RANTES, IL-4, GM-CSF, TNF-alpha, IL-6 and MIP-2 in lung tissue were significantly decreased when compared with the control OVA sensitized/challenged group. There was a significant decrease in BALF IL-4 only in the high-dose infliximab group.

CONCLUSIONS

These results show that an anti-TNF-alpha mAb has a considerable anti-inflammatory effect on allergen-induced lung inflammation in an animal model of acute asthma.