Important role of neutrophils in the late asthmatic response in mice

AimsNeutrophils have been found increasingly in the lungs of patients with severe asthma; however, it is unclear whether the neutrophils contribute to the induction of the airway obstruction. We determined using a murine model whether neutrophils are involved in the late asthmatic response (LAR), and analyzed mechanisms underlying the antigen-induced airway neutrophilia.Main methodsBALB/c mice sensitized by ovalbumin (OVA) + Al(OH)₃ were challenged 4 times by intratracheal administration of OVA. Airway mechanics were measured as specific airway resistance.Key findingsInduction of the LAR after the 4th challenge coincided with airway neutrophilia. In contrast, eosinophil infiltration was established prior to the 4th challenge. A treatment with an anti-Gr-1 monoclonal antibody (mAb) before the 4th challenge selectively suppressed increases in the neutrophil number and myeloperoxidase (MPO) level in bronchoalveolar lavage fluid (BALF), and attenuated the magnitude of LAR by 60–70%. Selective suppression of eosinophilia by anti-IL-5 mAb had little effect on the LAR. The increases in neutrophil number and MPO level were partially inhibited by an anti-CD4 mAb treatment. The CD4⁺ cell depletion also significantly inhibited increases in neutrophil chemoattractants, IL-17A, keratinocyte-derived chemokine (KC) and macrophage inflammatory protein (MIP)-2 in BALF. However, blockade of FcγRII/III failed to suppress the neutrophilia.SignificanceThese data suggest that neutrophils are key inducers of the LAR, and that the antigen-induced neutrophilia is partially dependent on activated CD4⁺ cells that are involved in the production of IL-17A, KC and MIP-2.     

Cutting edge: invariant V alpha 14 NKT cells are required for allergen-induced airway inflammation and hyperreactivity in an experimental asthma model

Airway hyperreactivity (AHR), eosinophilic inflammation with a Th2-type cytokine profile, and specific Th2-mediated IgE production characterize allergic asthma. In this paper, we show that OVA-immunized Jalpha18(-/-) mice, which are exclusively deficient in the invariant Valpha14(+) (iValpha14), CD1d-restricted NKT cells, exhibit impaired AHR and airway eosinophilia, decreased IL-4 and IL-5 production in bronchoalveolar lavage fluid, and reduced OVA-specific IgE compared with wild-type (WT) littermates. Adoptive transfer of WT iValpha14 NKT cells fully reconstitutes the capacity of Jalpha18(-/-) mice to develop allergic asthma. Also, specific tetramer staining shows that OVA-immunized WT mice have activated (CD69(+)) iValpha14 NKT cells. Importantly, anti-CD1d mAb treatment blocked the ability of iValpha14 T cells to amplify eosinophil recruitment to airways, and both Th2 cytokine and IgE production following OVA challenge. In conclusion, these findings clearly demonstrate that iValpha14 NKT cells are required to participate in allergen-induced Th2 airway inflammation through a CD1d-dependent mechanism.     

Neutrophil extracellular traps are downregulated by glucocorticosteroids in lungs in an equine model of asthma

Background

Severe neutrophilic asthma is poorly responsive to glucocorticosteroids (GC). Neutrophil extracellular traps (NETs) within the lungs have been associated with the severity of airway obstruction and inflammation in asthma, and were found to be unaffected by GC in vitro. As IL-17 is overexpressed in neutrophilic asthma and contributes to steroid insensitivity in different cell types, we hypothesized that NETs formation in asthmatic airways would be resistant to GC through an IL-17 mediated pathway.

Methods

Six neutrophilic severe asthmatic horses and six healthy controls were studied while being treated with dexamethasone. Lung function, bronchoalveolar lavage fluid (BALF) cytology and NETs formation, as well as the expression of CD11b and CD13 by blood and airway neutrophils were evaluated. The expression of IL-17 and its role in NETs formation were also studied.

Results

Airway neutrophils from asthmatic horses, as opposed to blood neutrophils, enhanced NETs formation, which was then decreased by GC. GC also tended to decrease the expression of CD11b in blood neutrophils, but not in airway neutrophils. IL-17 mRNA was increased in BALF cells of asthmatic horses and was unaffected by GC. However, both GC and IL-17 inhibited NETs formation in vitro.

Conclusion

GC decreased NETs formation in vitro and also in vivo in the lungs of asthmatic horses. However, airway neutrophil activation during asthmatic inflammation was otherwise relatively insensitive to GC. The contribution of IL-17 to these responses requires further study.

     

Flt-3 ligand reverses late allergic response and airway hyper-responsiveness in a mouse model of allergic inflammation

Flt3 ligand (Flt3-L) is a growth factor for dendritic cells and induces type 1 T cell responses. We recently reported that Flt3-L prevented OVA-induced allergic airway inflammation and suppressed late allergic response and airway hyper-responsiveness (AHR). In the present study we examined whether Flt3-L reversed allergic airway inflammation in an established model of asthma. BALB/c mice were sensitized and challenged with OVA, and AHR to methacholine was established. Then mice with AHR were randomized and treated with PBS or 6 microg of Flt3-L i.p. for 10 days. Pulmonary functions and AHR to methacholine were examined after rechallenge with OVA. Treatment with Flt3-L of presensitized mice significantly suppressed (p < 0.001) the late allergic response, AHR, bronchoalveolar lavage fluid total cellularity, absolute eosinophil counts, and inflammation in the lung tissue. There was a significant decrease in proinflammatory cytokines (TNF-alpha, IL-4, and IL-5) in bronchoalveolar lavage fluid, with a significant increase in serum IL-12 and a decrease in serum IL-5 levels. There was no significant effect of Flt3-L treatment on serum IL-4 and serum total IgE levels. Sensitization with OVA significantly increased CD11b(+)CD11c(+) cells in the lung, and this phenomenon was not significantly affected by Flt3-L treatment. These data suggest that Flt3-L can reverse allergic airway inflammation and associated changes in pulmonary functions in murine asthma model.     

Effector CD8+ T cells mediate inflammation and airway hyper-responsiveness

Allergic asthma is a complex syndrome characterized by airway obstruction, airway inflammation and airway hyper-responsiveness (AHR). Using a mouse model of allergen-induced AHR, we previously demonstrated that CD8-deficient mice develop significantly lower AHR, eosinophilic inflammation and interleukin (IL)-13 levels in bronchoalveolar lavage fluid compared with wild-type mice. These responses were restored by adoptive transfer of antigen-primed CD8(+) T cells. Previously, two distinct populations of antigen-experienced CD8(+) T cells, termed effector (T(EFF)) and central memory (T(CM)) cells, have been described. After adoptive transfer into CD8-deficient mice, T(EFF), but not T(CM), cells restored AHR, eosinophilic inflammation and IL-13 levels. T(EFF), but not T(CM), cells accumulated in the lungs, and intracellular cytokine staining showed that the transferred T(EFF) cells were a source of IL-13. These data suggest an important role for effector CD8(+) T cells in the development of AHR and airway inflammation, which may be associated with their Tc2-type cytokine production and their capacity to migrate into the lung.     

IL-17, produced by lymphocytes and neutrophils,is necessary for lipopolysaccharide-induced airway neutrophilia: IL-15 as a possible trigger

IL-17 is a cytokine implicated in the regulation of inflammation. We investigated the role of this cytokine in neutrophil recruitment using a model of LPS-induced lung inflammation in mice. In the bronchoalveolar lavage, LPS induced a first influx of neutrophils peaking at day 1, followed by a second wave, peaking at day 2. IL-17 levels were increased during the late phase neutrophilia (day 2), and this was concomitant with an increased number of T cells and macrophages, together with an increase of KC and macrophage-inflammatory protein-2 levels in the lung tissue. Intranasal treatment with a neutralizing murine anti-IL-17 Ab inhibited the late phase neutrophilia. In the bronchoalveolar lavage cells, IL-17 mRNA was detected at days 1, 2, and 3 postchallenge, with a strong expression at day 2. This expression was associated with CD4(+) and CD8(+) cells, but also with neutrophils. When challenged with LPS, despite the absence of T cells, SCID mice also developed a neutrophilic response associated with IL-17 production. In BALB/c mice, IL-15 mRNA, associated mainly with neutrophils, was evidenced 1 day after LPS challenge. In vitro, IL-15 was able to induce IL-17 release from purified spleen CD4(+) cells, but not spleen CD8(+) or airway neutrophils. We have shown that IL-17, produced mainly by CD4(+) cells, but also by neutrophils, plays a role in the mobilization of lung neutrophils following bacterial challenge. In addition, our results suggest that IL-15 could represent a physiological trigger that leads to IL-17 production following bacterial infection.     

Vaccination with allergen-IL-18 fusion DNA protects against, and reverses established, airway hyperreactivity in a murine asthma model

Vaccination with naked DNA encoding a specific allergen has been shown previously to prevent, but not reverse, the development of allergen-induced airway hyperresponsiveness (AHR). To enhance the effectiveness of DNA vaccine therapies and make possible the treatment of established AHR, we developed a DNA vaccination plasmid containing OVA cDNA fused to IL-18 cDNA. Vaccination of naive mice either with this fusion DNA construct or with an OVA cDNA-containing plasmid protected the mice from the subsequent induction of AHR. Protection from AHR correlated with increased IFN-gamma production and reduced OVA-specific IgE production. The protection appeared to be mediated by IFN-gamma and CD8(+) cells because treatment of mice with neutralizing anti-IFN-gamma mAb or with depleting anti-CD8 mAb abolished the protective effect. Moreover, vaccination of mice with preexisting AHR with the OVA-IL-18 fusion DNA, but not with the OVA cDNA plasmid, reversed established AHR, reduced allergen-specific IL-4, and increased allergen-specific IFN-gamma production. Thus, combining IL-18 cDNA with OVA cDNA resulted in a vaccine construct that protected against the development of AHR, and that was unique among cDNA constructs in its capacity to reverse established AHR.     

Matrix metalloproteinase-8 deficiency promotes granulocytic allergen-induced airway inflammation

Matrix metalloproteinases (MMPs) are involved in inflammatory reaction, including asthma-related airway inflammation. MMP-8, mainly produced by neutrophils, has recently been reported to be increased in the bronchoalveolar lavage fluid (BALF) from asthmatic patients. To evaluate the role of MMP-8 in asthma, we measured MMP-8 expression in lung tissue in an OVA-sensitized mouse model of asthma and addressed the effect of MMP-8 deletion on allergen-induced bronchial inflammation. MMP-8 production was increased in lungs from C57BL/6 mice exposed to allergens. After allergen exposure, MMP-8(-/-) mice developed an airway inflammation characterized by an increased neutrophilic inflammation in BALF and an increased neutrophilic and eosinophilic infiltration in the airway walls. MMP-8 deficiency was associated with increased levels of IL-4 and anti-OVA IgE and IgG1 in BALF and serum, respectively. Although allergen exposure induced an enhancement of LPS-induced CXC chemokine, KC, and MIP-2 levels in BALF and lung parenchyma, no difference was observed between the two genotypes. Inflammatory cell apoptosis was reduced in the lungs from MMP-8(-/-) mice. For the first time, our study evidences an important role of MMP-8 in the control of neutrophilic and eosinophilic infiltration during allergen-induced lung inflammation, and demonstrates that the anti-inflammatory effect of MMP-8 is partly due to a regulation of inflammatory cell apoptosis.     

Naturally occurring lung CD4(+)CD25(+) T cell regulation of airway allergic responses depends on IL-10 induction of TGF-beta

Peripheral tolerance to allergens is mediated in large part by the naturally occurring lung CD4(+)CD25(+) T cells, but their effects on allergen-induced airway responsiveness have not been well defined. Intratracheal, but not i.v., administration of naive lung CD4(+)CD25(+) T cells before allergen challenge of sensitized mice, similar to the administration of the combination of rIL-10 and rTGF-beta, resulted in reduced airway hyperresponsiveness (AHR) and inflammation, lower levels of Th2 cytokines, higher levels of IL-10 and TGF-beta, and less severe lung histopathology. Significantly, CD4(+)CD25(+) T cells isolated from IL-10(-/-) mice had no effect on AHR and inflammation, but when incubated with rIL-10 before transfer, suppressed AHR, and inflammation, and was associated with elevated levels of bronchoalveolar lavage TGF-beta levels. By analogy, anti-TGF-beta treatment reduced regulatory T cell activity. These data identify naturally occurring lung CD4(+)CD25(+) T cells as capable of regulating lung allergic responses in an IL-10- and TGF-beta-dependent manner.     

Contribution of antigen-primed CD8+ T cells to the development of airway hyperresponsiveness and inflammation is associated with IL-13

The role of Th2/CD4 T cells, which secrete IL-4, IL-5, and IL-13, in allergic disease is well established; however, the role of CD8(+) T cells (allergen-induced airway hyperresponsiveness (AHR) and inflammation) is less clear. This study was conducted to define the role of Ag-primed CD8(+) T cells in the development of these allergen-induced responses. CD8-deficient (CD8(-/-)) mice and wild-type mice were sensitized to OVA by i.p. injection and then challenged with OVA via the airways. Compared with wild-type mice, CD8(-/-) mice developed significantly lower airway responsiveness to inhaled methacholine and lung eosinophilia, and exhibited decreased IL-13 production both in vivo, in the bronchoalveolar lavage (BAL) fluid, and in vitro, following Ag stimulation of peribronchial lymph node (PBLN) cells in culture. Reconstitution of sensitized and challenged CD8(-/-) mice with allergen-sensitized CD8(+) T cells fully restored the development of AHR, BAL eosinophilia, and IL-13 levels in BAL and in culture supernatants from PBLN cells. In contrast, transfer of naive CD8(+) T cells or allergen-sensitized CD8(+) T cells from IL-13-deficient donor mice failed to do so. Intracellular cytokine staining of lung as well as PBLN T cells revealed that CD8(+) T cells were a source of IL-13. These data suggest that Ag-primed CD8(+) T cells are required for the full development of AHR and airway inflammation, which appears to be associated with IL-13 production from these primed T cells.     

Resolution of Der p1-induced allergic airway inflammation is dependent on CD4+CD25+Foxp3+ regulatory cells

Allergic airway inflammation (AAI) is characterized by airway hyperreactivity, eosinophilia, goblet cell hyperplasia, and elevated serum IgE, however, it is unclear what mediates natural resolution after cessation of allergen exposure. This is important because the outcome of subsequent allergen challenge may depend on the concurrent inflammatory milieu of the lung. Using a murine AAI model, we demonstrate that after exposure to a defined natural protein allergen, Der p1, the response in lungs and draining mediastinal lymph nodes (dMLN) peaks between 4 and 6 days then declines until resolution by 21 days. Der p1-specific serum IgE follows the same pattern while IgG1 continues to increase. Resolution of AAI is mediated by CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs), which appear in lungs and dMLN following airway challenge. Treg depletion exacerbated lung eosinophilia, increased dMLN IL-5 and IL-13 but not IL-10 secretion, and increased allergic Ab responses. Most convincingly, transfer of CD4(+)CD25(+)Foxp3(+) T cells from Ag naive mice (natural Tregs) abolished AAI, decreased dMLN IL-5 and IL-13 secretion, increased dMLN IL-10 secretion, abolished IgE, and decreased IgG1 Abs. Blocking IL-10 receptor function in vivo did not block the anti-inflammatory function of transferred natural Tregs but did restore dMLN IL-5 and IL-13 secretion. Thus natural Tregs can control AAI in an IL-10 independent manner.     

ATP binding cassette transporter G1 deletion induces IL-17-dependent dysregulation of pulmonary adaptive immunity

Mice with genetic deletion of the cholesterol transporter ATP binding cassette G1 (ABCG1) have pulmonary lipidosis and enhanced innate immune responses in the airway. Whether ABCG1 regulates adaptive immune responses to the environment is unknown. To this end, Abcg1(+/+) and Abcg1(-/-) mice were sensitized to OVA via the airway using low-dose LPS as an adjuvant, and then challenged with OVA aerosol. Naive Abcg1(-/-) mice displayed increased B cells, CD4(+) T cells, CD8(+) T cells, and dendritic cells (DCs) in lung and lung-draining mediastinal lymph nodes, with lung CD11b(+) DCs displaying increased CD80 and CD86. Upon allergen sensitization and challenge, the Abcg1(-/-) airway, compared with Abcg1(+/+), displayed reduced Th2 responses (IL-4, IL-5, eosinophils), increased neutrophils and IL-17, but equivalent airway hyperresponsiveness. Reduced Th2 responses were also found using standard i.p. OVA sensitization with aluminum hydroxide adjuvant. Mediastinal lymph nodes from airway-sensitized Abcg1(-/-) mice produced reduced IL-5 upon ex vivo OVA challenge. Abcg1(-/-) CD4(+) T cells displayed normal ex vivo differentiation, whereas Abcg1(-/-) DCs were found paradoxically to promote Th2 polarization. Th17 cells, IL-17(+) γδT cells, and IL-17(+) neutrophils were all increased in Abcg1(-/-) lungs, suggesting Th17 and non-Th17 sources of IL-17 excess. Neutralization of IL-17 prior to challenge normalized eosinophils and reduced neutrophilia in the Abcg1(-/-) airway. We conclude that Abcg1(-/-) mice display IL-17-mediated suppression of eosinophilia and enhancement of neutrophilia in the airway following allergen sensitization and challenge. These findings identify ABCG1 as a novel integrator of cholesterol homeostasis and adaptive immune programs.     

Role of mast cells and basophils in IgE responses and in allergic airway hyperresponsiveness

We established a diphtheria toxin (DT)-based conditional deletion system using Il4 enhancer elements previously shown to be specific for IL-4 production in mast cells (MCs) or basophils (Mas-TRECK and Bas-TRECK mice). DT treatment of Bas-TRECK mice resulted in specific deletion of basophils, whereas both MCs and basophils were deleted in Mas-TRECK mice. DT-treated Mas-TRECK mice had impaired passive cutaneous anaphylaxis, IgE-mediated passive systemic anaphylaxis, and IgE-mediated chronic allergic inflammation, whereas DT-treated Bas-TRECK mice had impaired IgE-mediated chronic allergic inflammation. Using these mice, we also sought to tease out the role of MCs and basophils in airway hyperresponsiveness (AHR). Although MC deletion resulted in a slight increase in basal Ag-specific IgE levels and significant increases in basal IgE levels, we found that this deletion markedly impaired the AHR effector phase and was accompanied by decreased histamine levels. By contrast, basophil deletion had no effect on the AHR effector phase or on IgE production induced by systemic OVA immunization. Our results, using these newly established Mas-TRECK and Bas-TRECK models, demonstrated an indispensable role for MCs as effector cells in AHR.     

Vaccination with heat-killed Listeria as adjuvant reverses established allergen-induced airway hyperreactivity and inflammation: role of CD8+ T cells and IL-18

Asthma is a respiratory disorder characterized by airway hyperreactivity (AHR) and inflammation and is associated with high serum IgE and overproduction of IL-4, IL-5, and IL-13 by allergen-specific Th2 cells. Our previous studies demonstrated that heat-killed Listeria monocytogenes (HKL) as an adjuvant in immunotherapy successfully reversed ongoing Ag-specific Th2-dominated responses toward Th1-dominated responses, but it was unclear if such immune modulation could reverse ongoing, established disease in target organs such as the lung. In this paper we show that a single dose of Ag plus HKL as adjuvant significantly reduced AHR in a murine model for asthma and reversed established AHR when given late after allergen sensitization. HKL as adjuvant also dramatically inhibited airway inflammation, eosinophilia, and mucus production, significantly reduced Ag-specific IgE and IL-4 production, and dramatically increased Ag-specific IFN-gamma synthesis. The inhibitory effect of HKL on AHR depended on the presence of IL-12 and CD8+ T cells and was associated with an increase of IL-18 mRNA expression. Thus, our results demonstrate that HKL as an adjuvant for immunotherapy mediates immune deviation from a pathological Th2-dominated response toward a protective immune response in peripheral lymphoid tissues and in the lungs and may be clinically effective in the treatment of patients with established asthma and allergic disease.     

MHC class II-associated invariant chain isoforms regulate pulmonary immune responses

Asthma, a chronic inflammatory disease of the lung, is characterized by reversible airway obstruction and airway hyperresponsiveness (AHR), and is associated with increased production of IgE and Th2-type cytokines (IL-4, IL-5, and IL-13). Development of inflammation within the asthmatic lung depends on MHC class II-restricted Ag presentation, leading to stimulation of CD4(+) T cells and cytokine generation. Conventional MHC class II pathways require both MHC-associated invariant chain (Ii) and HLA-DM (H2-M in mice) chaperone activities, but alternative modes of Ag presentation may also promote in vivo immunity. In this study, we demonstrate that Ii(-/-) and H2-M(-/-) mice fail to develop lung inflammation or AHR following sensitization and challenge with OVA in a mouse model of allergic inflammation. To assess potentially distinct contributions by Ii chain isoforms to lung immunity, we also compared allergen-induced lung inflammation, eosinophilia, IgE production, and AHR in mice genetically altered to express either p31 Ii or p41 Ii isoform alone. Sole expression of either Ii isoform alone facilitates development of allergen-induced lung inflammation and eosinophilia. However, animals expressing only the p31 Ii isoform exhibit abrogated IgE and AHR responses as compared with p41 Ii mice in this model of allergen-induced lung inflammation, suggesting that realization of complete immunity within the lung requires expression of p41 Ii. These findings reveal a crucial role of Ii and H2-M in controlling the immune response within the lung, and suggest that p31 Ii and p41 Ii manifest nonredundant roles in development of immunity.     

Intrinsic AHR in IL-5 transgenic mice is dependent on CD4(+) cells and CD49d-mediated signaling

Overexpression of interleukin (IL)-5 by the airway epithelium in mice using the rat CC10 promoter (NJ.1726 line) leads to several histopathologies characteristic of human asthma, including airway hyperreactivity (AHR). We investigated the contribution of B and T cells, as well as CD4 expression, to the development of AHR in IL-5 transgenic mice. NJ.1726 mice on a T cell or CD4 knockout background, but not on a B cell knockout background, lost intrinsic AHR. These effects occurred without decreases in IL-5 or eosinophils. We further investigated the contribution of alpha(4)-integrin signaling to the development of AHR in IL-5 transgenic mice through the administration of anti-CD49d (alpha(4)-integrin) antibody (PS/2). Administration of PS/2 resulted in immediate (16-h) inhibition of AHR. The inhibition of AHR was not associated with a decrease in airway eosinophils. These studies demonstrate that, despite the presence of increased levels of IL-5 and eosinophils in the lungs of NJ.1726 mice, CD4(+) cells and alpha(4)-integrin signaling are necessary for the intrinsic AHR that develops in IL-5 transgenic mice.     

Human neutrophils express the high-affinity receptor for immunoglobulin E (Fc epsilon RI): role in asthma.

Polymorphonuclear neutrophils (PMNs) are important effector cells in host defense and the inflammatory response to antigen. The involvement of PMNs in inflammation is mediated mainly by the Fc receptor family, including IgE receptors. Recently, PMNs were shown to express two IgE receptors (CD23/Fc epsilon RII and galectin-3). In allergic diseases, the dominant role of IgE has been mainly ascribed to its high-affinity receptor, Fc epsilon RI. We have examined the expression of Fc epsilon RI by PMNS: mRNA and cell surface expression of Fc epsilon RI alpha chain was identified on PMNs from asthmatic subjects. Furthermore, preincubation with human IgE Fc fragment blocks completely the binding of anti-Fc epsilon RI alpha chain (mAb15--1) to human PMNS: Conversely, preincubation of PMNs with mAb15--1 inhibits significantly the binding of IgE Fc fragment to PMNs, indicating that IgE bound to the cell surface of PMNs mainly via the Fc epsilon RI. Peripheral blood and bronchoalveolar lavage (BAL) PMNs from asthmatic subjects also express intracellular Fc epsilon RI alpha and beta chain immunoreactivity. Engagement of Fc epsilon RI induces the release of IL-8 by PMNS: Collectively, these observations provide new evidence that PMNs express the Fc epsilon RI and suggest that these cells may play a role in allergic inflammation through an IgE-dependent activation mechanism.     

IL-17-producing alveolar macrophages mediate allergic lung inflammation related to asthma

IL-17 is a pivotal proinflammatory molecule in asthmatics. However, the cellular source of IL-17 in asthma has not been identified to date. In this study, we report that macrophages rather than Th17 cells are the main producer of IL-17 in allergic inflammation related to asthma. After OVA challenge in a mouse model mimicking allergic asthma, the increased IL-17(+) cells in the lung were mainly CD11b(+)F4/80(+) macrophages, instead of T cells or others. Importantly, IL-17(+) alveolar macrophages (AMs), but not IL-17(+) interstitial macrophages, were significantly increased after allergen challenge. The increase of IL-17(+) AMs was not due to the influx of IL-17(+) macrophages from circulation or other tissues, but ascribed to the activation of AMs by mediator(s) secreted by IgE/OVA-activated mast cells. Depleting alveolar macrophages or neutralizing IL-17 prevented the initiation of OVA-induced asthma-related inflammation by inhibiting the increase of inflammatory cells and inflammatory factors in bronchoalveolar lavage fluid. Th2 cytokine IL-10 could down-regulate IL-17 expression in alveolar macrophages. The increased IL-17 and the decreased IL-10 in bronchoalveolar lavage fluid were further confirmed in asthmatic patients. These findings suggest that IL-17 is mainly produced by macrophages but not Th17 cells in allergic inflammation related to asthma. Mast cell-released mediators up-regulate the expression of IL-17 by macrophages, whereas IL-10 down-regulates IL-17 expression.     

Local expansion of allergen-specific CD30+Th2-type gamma delta T cells in bronchial asthma.

BACKGROUND: T lymphocytes infiltrating airways during the allergic immune response play a fundamental role in recruiting other specialized cells, such as eosinophils, by secreting interleukin 5 (IL-5), and promoting local and systemic IgE synthesis by producing IL-4. Whether these presumed allergen-specific T cells are of mucosal or systemic origin is still a matter of conjecture. MATERIALS AND METHODS: Immunophenotype, IL-4 production, and in vitro proliferative response to specific or unrelated allergens were analyzed in the bronchoalveolar lavage (BAL) fluid lymphocyte suspensions obtained from untreated patients with allergic asthma. Healthy subjects and patients affected by pulmonary sarcoidosis, a granulomatous lung disease characterized by infiltrating Th1 CD4+ lymphocytes, served as controls. RESULTS: The proportions of gamma delta T lymphocytes, mostly CD4+ or CD4- (-)CD8-, was higher in asthmatic subjects than in controls (p < 0.05). Most BAL gamma delta CD4+ lymphocytes of asthmatic patients displayed the T cell receptor (TCR)-gamma delta V delta 1 chain. While CD30 antigen coexpression on the surface of BAL alpha beta(+) T lymphocytes was low (ranging from 5 to 12%), about half of pulmonary gamma delta T cells coexpressed it. These cells produced IL-4 and negligible amounts of interferon-gamma (IFN gamma), and proliferated in vitro in response to purified specific but not unrelated allergens. In contrast, control or sarcoidosis gamma delta T cells never displayed the CD30 surface molecule or produced significant quantities of IL-4. CONCLUSIONS: These findings not only confirm our previous hypothesis that the allergen-specific Th2-type lymphocytes found in the lungs of asthmatic patients are gamma delta T cells belonging to airway mucosal immunocytes, but also strongly support the notion that asthma is a local rather than a systemic disease.