Airway Immune Responses Research Articles

Interactions between epithelial cells and dendritic cells in airway immune responses: lessons from allergic airway disease

Micro-organisms constantly invade the human body and may form a threat to our health. Traditionally, concepts of defence mechanisms have included a protective outer layer of epithelia and a vigilant immune system searching for areas where the integrity of the outer layer may be compromised. Instead of considering these elements as two independent mechanisms, we should be treating them as a single integrated system. This review will present and discuss the role of local immune-competent cells and local epithelia in the recognition of potential pathogens and how the interaction between the two components may affect the initiation of the airway immune response. A concept emerges where airway mucosal dendritic cells act as integrators of both immunostimulatory and immunosuppressive signals that act within actively-involved mucosal tissue.

4-1BB Engagement Costimulates NKT Cell Activation and Exacerbates NKT Cell Ligand-Induced Airway Hyperresponsiveness and Inflammation

Multiple studies have demonstrated that 4-1BB (CD137), a member of the TNF receptor superfamily, is expressed on several immune cells including activated T cells. However, the expression and the role of 4-1BB on natural killer T (NKT) cells have not been fully characterized. In this study, it was shown that 4-1BB was not expressed on naive NKT cells but was rapidly induced on activated NKT cells by TCR engagement with alpha-galactosylceramide (alpha-GalCer). Also, 4-1BB signaling provided by 3H3, an agonistic anti-4-1BB mAb, promoted NKT cell activation resulting in enhanced cytokine production of NKT cells driven by alpha-GalCer. When NKT cell-driven airway immune responses were evaluated by intranasal administration of alpha-GalCer, airway hyperresponsiveness (AHR) and lung inflammation were significantly more aggravated in mice treated with 3H3 and alpha-GalCer than in mice treated with alpha-GalCer alone. These aggravations were accompanied by up-regulation of IL-4, IL-13, and IFN-gamma production. Interestingly, AHR was not developed in IL-4Ralpha-deficient mice treated with alpha-GalCer with or without 3H3 but was exacerbated in IFN-gamma-deficient mice. Our study suggests that 4-1BB on NKT cells functions as a costimulatory molecule and exacerbates the induction of NKT cell-mediated AHR, which is dependent on the IL-4Ralpha-mediated pathway.

Injury Stimulates an Innate Respiratory Immunoglobulin A Immune Response in Humans

Secretory immunoglobulin A (SIgA) is the specific immune antibacterial defense. Since pneumonia frequently complicates the course of trauma patients, we studied early airway immune responses after injury. Twelve severely injured, intubated (expected for >/=5 d) patients had tracheal and bilateral lung lavage (BAL) within 30 hours of injury (n = 12). Epithelial lining fluid (ELF) volume and SIgA were measured by urea dilution and enzyme-linked immunosorbent assay (ELISA), respectively. Control BAL specimens were obtained from eight healthy elective surgical patients. Anatomically based comparisons were made between groups with Welch's unpaired t test. To verify human data, 30 male mice received no injury (time 0, n = 7) or injury with abdominal and neck incisions and were killed for airway IgA at 4 (n = 7), 8 (n = 8), and 24 (n = 8) hours. Analysis of variance (ANOVA) and Fisher's protected least significant difference testing was used to analyze animal data. Initial trauma patient SIgA concentration (SIgA/mL ELF) increased compared with control in the lungs bilaterally (p < 0.05 both right and left). ELF volume was significantly higher in the right lung (p = 0.02) and just missed statistical significance (p = 0.07) on the left. Mouse IgA increased 8 hours after stress (p < 0.05 versus 0, 4, and 24 hours) and returned to normal by 24 hours. A previously unrecognized innate human airway mucosal immune response with increased airway SIgA and ELF occurs after severe injury and is reproducible experimentally. This accessible, quantifiable human response allows study of clinical strategies to reduce infections via mucosal immune therapies.

Regulation of Airway Innate and Adaptive Immune Responses: The IL-17 Paradigm

IL-17 is a proinflammatory cytokine produced by immune cells. Its significance in host defense and disease development has been demonstrated in various infection and autoimmune models. Recently, additional studies have shown that IL-17 is also important in modulating airway immune response in several aspects. Along with the well-established Th1/Th2 model, new discoveries regarding the Th17 lineage and IL-17 functions have added an extra twist to the already complicated cytokine network that regulates airway immunity. The IL-17 receptor is expressed on blood cells, as well as on structural cells such as the epithelial cells in the airway. Therefore, the effect of IL-17 on airway immunity is very broad, covering both the innate and the adaptive aspects. In this review, we summarize the findings of recent studies on IL-17 signaling and function in pulmonary immune response, and the implications of IL-17 in disease pathogenesis.

Suppression of allergen-induced airway inflammation and immune response by the peroxisome proliferator-activated receptor-alpha agonist fenofibrate

In the present study, we have assessed the effect of the peroxisome proliferator-activated receptor-α (PPARα) agonist fenofibrate on allergen-induced airway inflammation and immune response. C57BL/6 or PPARα knock-out (PPARα −/−) mice were sensitized with ovalbumin and challenged with ovalbumin alone or with ovalbumin + lipopolysaccharides. Fenofibrate was administered to allergen-exposed animals during challenge only or from the day prior to sensitization to the end of challenge. Inflammation and immune response were assessed by determining cell counts and cytokine levels in bronchoalveolar lavage fluids, expression of the transcription factors Gata-3 and T-bet in lung tissue and ovalbumin-specific IgE and IgG2a in serum. Treatment with fenofibrate (0.15–15 mg/day) during allergen challenge dose-dependently reduced airway inflammatory cell infiltrate induced by ovalbumin in C57BL/6 mice. Reduction reached 74.3% ( P < 0.001) in animals treated with 15 mg/day of the PPARα agonist, whereas this treatment failed to suppress cell infiltrate induced by allergen in PPARα −/− mice. In addition, when administered from the day prior to sensitization to the end of challenge, fenofibrate (15 mg/day) triggered switching of the immune response to allergen towards a Th1 profile, as evidenced by an increase in IgG2a levels, a reduction in IL(interleukin)-4 and IL-5 together with an increase in interferon-γ, and a decrease in Gata-3/T-bet expression ratio. Upon challenge with ovalbumin + lipopolysaccharides, sensitized mice developed a severe inflammatory response characterized by infiltration of eosinophils, neutrophils, lymphocytes and macrophages and by increased release of IL-4, IL-5, tumor necrosis factor-α, macrophage-inflammatory protein-2 and monocyte chemoattractant protein-1. Administration of fenofibrate during allergen challenge dramatically reduced all responses. In conclusion, our data clearly demonstrate that fenofibrate exhibits an anti-inflammatory activity in allergic asthma, including in severe conditions, and that the PPARα agonist is also capable of switching the immune response to allergen towards a Th1 profile when given from the day prior to sensitization.

Expression of activated FcγRII discriminates between multiple granulocyte-priming phenotypes in peripheral blood of allergic asthmatic subjects

Allergic asthma is associated with chronic airway and systemic immune responses. Systemic responses include priming of peripheral blood eosinophils, which is enhanced after allergen challenge. In a subpopulation of asthmatic subjects, neutrophils are associated with bronchial inflammation. We sought to monitor systemic granulocyte priming in allergic asthmatic subjects as a consequence of chronic and acute inflammatory signals initiated by allergen challenge. Blood was taken at baseline and 6 to 24 hours after allergen challenge in asthmatic subjects with and without late asthmatic responses. Systemic granulocyte priming was studied by using expression of cellular markers, such as alpha-chain of Mac-1 (alpha m)/CD11b, L-selectin/CD62L, and an activation epitope present on Fc gamma RII/CD32 recognized by monoclonal phage antibody A17. Eosinophils of asthmatic subjects have a primed phenotype identified by cell-surface markers. Neutrophils of these patients were subtly primed, which was only identified after activation with N-formyl-methionyl-leucyl-phenylalanine. After allergen challenge, an acute increase in eosinophil priming characterized by enhanced expression of activated Fc gamma RII was found in patients experiencing a late asthmatic response and not in patients with a single early asthmatic response. In contrast, expression of alpha m/CD11b and L-selectin on granulocytes was not different between control and asthmatic subjects and was not affected by allergen challenge. Interestingly, expression of both adhesion molecules was positively correlated, and alpha m expression on eosinophils and neutrophils correlated positively with bronchial hyperresponsiveness. Different phases, phenotypes, or both of allergic asthma are associated with distinct priming profiles of inflammatory cells in peripheral blood. Insight in differences of systemic innate responses will lead to better definition of asthma subtypes and to better designs of new therapeutic options.

Expression and selective up-regulation of toxin-related mono ADP-ribosyltransferases by pathogen-associated molecular patterns in alveolar epithelial cells

Mono ADP-ribosyltransferases (ARTs) are a family of enzymes related to bacterial toxins that possess adenosine diphosphate ribosyltransferase activity. We have assessed that A549 constitutively expressed ART1 on the cell surface and shown that lipotheicoic acid (LTA) and flagellin, but not lipopolysaccharide (LPS), peptidoglycan (PG) and poly (I:C), up-regulate ART1 in a time and dose dependent manner. These agonists did not alter the expression of ART3 and ART5 genes. Indeed, LTA and flagellin stimulation increased the level of ART1 protein and transcript while ART4 gene was activated after stimulation of cells with LPS, LTA, PAM and PG via TLR2 and TLR4 receptors. These results show that human ARTs possess a differential capacity to respond to bacteria cell wall components and might play a crucial role in innate immune response in airways.

Multiple Granulocyte Priming Phenotypes In Peripheral Blood Of Allergic Asthmatics

RATIONALE: Allergic asthma is associated with chronic airway and systemic immune responses. Systemic responses include priming of peripheral blood eosinophils, which is enhanced after allergen challenge. In a subpopulation of asthmatics neutrophils are associated with bronchial inflammation. The objective of this study was to monitor granulocyte priming in allergic asthmatics as consequence of chronic and acute inflammatory signals initiated by allergen challenge.METHODS: Blood was taken at baseline and 6-72h after allergen challenges in asthmatics with and without late asthmatic responses (LAR). Systemic granulocyte priming was studied using 1) expression of cellular markers such as αm (CD11b), L-selectin and a priming epitope recognized by monoclonal phage antibody A17 and 2) gene expression profiles in neutrophils.RESULTS: Eosinophils of asthmatics have a primed phenotype identified using cellular surface markers. Neutrophils of asthmatics were subtle primed, which was only identified using gene expression profiling. After allergen challenge, an acute increase in eosinophil and neutrophil priming was found only in patients experiencing a LAR using priming markers and gene expression analysis, respectively. In contrast, granulocyte αm (CD11b) and L-selectin levels were not different between controls and asthmatics and not affected by allergen challenge. Interestingly, expression of both adhesion molecules was positively correlated and αm expression on eosinophils and neutrophils correlated positively with bronchial hyperresponsiveness.CONCLUSION: Different phases and/or phenotypes of allergic asthma are associated with distinct priming profiles of inflammatory cells in peripheral blood. Insight in differences of systemic innate responses will lead to better definition of asthma-subtypes and to better designs of new therapeutic options. RATIONALE: Allergic asthma is associated with chronic airway and systemic immune responses. Systemic responses include priming of peripheral blood eosinophils, which is enhanced after allergen challenge. In a subpopulation of asthmatics neutrophils are associated with bronchial inflammation. The objective of this study was to monitor granulocyte priming in allergic asthmatics as consequence of chronic and acute inflammatory signals initiated by allergen challenge. METHODS: Blood was taken at baseline and 6-72h after allergen challenges in asthmatics with and without late asthmatic responses (LAR). Systemic granulocyte priming was studied using 1) expression of cellular markers such as αm (CD11b), L-selectin and a priming epitope recognized by monoclonal phage antibody A17 and 2) gene expression profiles in neutrophils. RESULTS: Eosinophils of asthmatics have a primed phenotype identified using cellular surface markers. Neutrophils of asthmatics were subtle primed, which was only identified using gene expression profiling. After allergen challenge, an acute increase in eosinophil and neutrophil priming was found only in patients experiencing a LAR using priming markers and gene expression analysis, respectively. In contrast, granulocyte αm (CD11b) and L-selectin levels were not different between controls and asthmatics and not affected by allergen challenge. Interestingly, expression of both adhesion molecules was positively correlated and αm expression on eosinophils and neutrophils correlated positively with bronchial hyperresponsiveness. CONCLUSION: Different phases and/or phenotypes of allergic asthma are associated with distinct priming profiles of inflammatory cells in peripheral blood. Insight in differences of systemic innate responses will lead to better definition of asthma-subtypes and to better designs of new therapeutic options.

Analysis of Airway Immune System Responses to Rhinovirus Infection in Children and Resultant Tendency to Wheeze

Analysis of Airway Immune System Responses to Rhinovirus Infection in Children and Resultant Tendency to Wheeze

Diesel Exhaust Particle-Exposed Human Bronchial Epithelial Cells Induce Dendritic Cell Maturation

Increased exposure to air pollutants such as diesel exhaust particles (DEP) has been proposed as one mechanism to explain the rise in allergic disorders. However, the immunologic mechanisms by which DEP enhance allergic sensitization and asthma remain unclear. We hypothesized that DEP act as an adjuvant for immature dendritic cell (DC) maturation via its effect on airway epithelial cell-derived microenvironment for DC. Immature monocyte-derived DC (iMDDC) failed to undergo phenotypic (CD80, CD83, CD86) or functional (T cell activation) maturation in response to exposure to DEP (0.001-100 mug/ml). In contrast, primary cultures of human bronchial epithelial cells (HBEC) treated with DEP induced iMDDC phenotypic maturation (2.6 +/- 0.1-fold increase in CD83 expression, n = 4, p < 0.05) and functional maturation (2.6 +/- 0.2-fold increase in T cell activation, n = 4, p < 0.05). Functional maturation of iMDDC was induced by conditioned medium derived from DEP-treated HBEC, and was inhibited in cultures with DEP-treated HBEC and blocking Abs against GM-CSF, or GM-CSF-targeted small interfering RNA. These data suggest that DEP induce Ag-independent DC maturation via epithelial cell-DC interactions mediated by HBEC-derived GM-CSF. Although additional signals may be required for polarization of DC, these data suggest a novel mechanism by which environmental pollutants alter airway immune responses.

Mainstream Cigarette Smoke Exposure Attenuates Airway Immune Inflammatory Responses to Surrogate and Common Environmental Allergens in Mice, Despite Evidence of Increased Systemic Sensitization

The purpose of this study was to investigate the impact of mainstream cigarette smoke exposure (MTS) on allergic sensitization and the development of allergic inflammatory processes. Using two different experimental murine models of allergic airways inflammation, we present evidence that MTS increased cytokine production by splenocytes in response to OVA and ragweed challenge. Paradoxically, MTS exposure resulted in an overall attenuation of the immune inflammatory response, including a dramatic reduction in the number of eosinophils and activated (CD69+) and Th2-associated (T1ST2+) CD4 T lymphocytes in the lung. Although MTS did not impact circulating levels of OVA-specific IgE and IgG1, we observed a striking reduction in OVA-specific IgG2a production and significantly diminished airway hyperresponsiveness. MTS, therefore, plays a disparate role in the development of allergic responses, inducing a heightened state of allergen-specific sensitization, but dampening local immune inflammatory processes in the lung.

Mononuclear cell subsets in bronchoalveolar lavage fluid duringDictyocaulus viviparusinfection of calves: a potential role for γ/δ TCR‐expressing cells in airway immune responses?

Mononuclear cell populations in the lungs of calves infected with Dictyocaulus viviparus were studied during primary infection and reinfection in order to identify cells involved in development of protective immunity to parasitic bronchitis. Three groups of calves were either inoculated with 500 third-stage larvae at both weeks 0 and 10 (n = 6), inoculated only at week 10 (n = 6), or remained uninfected (n = 3). The animals were monitored weekly by collection of bronchoalveolar lavage fluid (BALF), blood and faeces. Among mononuclear BALF-cell populations, the gamma/delta TCR-expressing cells showed a pronounced transient increase in proportion as well as in relative cell size 2 weeks post primary infection, whereas CD4-, CD8-, Ig- and CD14-expressing cells showed no significant differences related to the infection. The increase in gamma/delta TCR-expressing cells coincided with significantly increased proportions of eosinophils and recovery of adult worms in BALF. After reinfection, gamma/delta TCR-expressing cells increased again, but not until week 3 post inoculation, whereas eosinophils were increased by week 2 and reached higher levels than after primary infection. After reinfection, establishment of D. viviparus was less successful than after primary infection. In conclusion, these results indicate a role for gamma/delta TCR-expressing lymphocytes in the pathogenesis of D. viviparus infection.

Obesity and asthma, what are the links?

Obesity is a major cause of morbidity accounting for approximately 300 000 deaths each year and about 7% of the health care budget with an economic impact greater than US dollar 100 billion annually in the United States. Obesity and its sequelae such as cardiovascular disease, diabetes, arthritis or cancer have been on the rise over the last decades. The parallel time trend with an increasing prevalence of asthma has induced a lively debate about a potential link between both conditions. A number of prospective studies have shown that weight gain can antedate the development of asthma. Effect modification by sex may occur as some studies have shown effects of body mass index on asthma only among females. However, sex differences are not consistent. Several hypotheses have been proposed to explain the epidemiological associations including alterations in airway mechanics and immune responses, hormonal influences and genetic factors. There is evidence that obesity and overweight are associated with the development of asthma. Yet, the mechanisms underlying this relation are unclear. Weight reduction among asthmatic patients can result in improvements of lung function demonstrating the potential clinical impact of the findings.

Effect of fungal antigen exposure on airway allergen sensitization

RATIONALE: Repeated exposure to innocuous antigens often induces immunologic tolerance unless if primed with an adjuvant. Fungi, such as Alternaria and Candida, are ubiquitous in the air and their potential pro-inflammatory properties could overcome immunologic tolerance. In this study, we examined the effect of Alternaria and Candida on the airway immune response to OVA using a mouse model.METHODS: BALB/c female mice were exposed intranasally on days 0 and 7 with fungal extracts (Alternaria alternata or Candida albicans), either alone or in combination with OVA. Plasma was obtained on day 14 for measurement of total and OVA-specific IgE and IgG1. The mice were challenged intranasally with OVA on days 21, 22 and 23. Bronchoalveolar lavage fluid was collected on day 24 and analyzed for airway inflammation.RESULTS: Mice exposed to both Alternaria and OVA developed more OVA-specific IgE (0.098±0.034 absorbance at 450 nm (O.D); p=0.053) and IgG1 (0.347±0.033 O.D; p<0.001), and a robust eosinophilic airway inflammatory response (19.8±6.7% of total BAL cells; p<0.05) compared to mice exposed to OVA alone (0.011±0.003, 0.046±0.027 and 2.5±1.3%, respectively). In contrast, mice exposed to both Candida and OVA produced no increase in OVA-specific IgE or IgG1. Furthermore, airway neutrophilia, and not eosinophilia, was observed when mice previously exposed to Candida plus OVA were subsequently exposed to OVA.CONCLUSIONS: Alternaria, but not Candida, is a potent catalyst for Th2-like acquired immunity to bystander antigens. The ability of ubiquitous fungi to enhance airway immune response to bystander antigens may play an important role in mounting an allergic response to aeroallergen. RATIONALE: Repeated exposure to innocuous antigens often induces immunologic tolerance unless if primed with an adjuvant. Fungi, such as Alternaria and Candida, are ubiquitous in the air and their potential pro-inflammatory properties could overcome immunologic tolerance. In this study, we examined the effect of Alternaria and Candida on the airway immune response to OVA using a mouse model. METHODS: BALB/c female mice were exposed intranasally on days 0 and 7 with fungal extracts (Alternaria alternata or Candida albicans), either alone or in combination with OVA. Plasma was obtained on day 14 for measurement of total and OVA-specific IgE and IgG1. The mice were challenged intranasally with OVA on days 21, 22 and 23. Bronchoalveolar lavage fluid was collected on day 24 and analyzed for airway inflammation. RESULTS: Mice exposed to both Alternaria and OVA developed more OVA-specific IgE (0.098±0.034 absorbance at 450 nm (O.D); p=0.053) and IgG1 (0.347±0.033 O.D; p<0.001), and a robust eosinophilic airway inflammatory response (19.8±6.7% of total BAL cells; p<0.05) compared to mice exposed to OVA alone (0.011±0.003, 0.046±0.027 and 2.5±1.3%, respectively). In contrast, mice exposed to both Candida and OVA produced no increase in OVA-specific IgE or IgG1. Furthermore, airway neutrophilia, and not eosinophilia, was observed when mice previously exposed to Candida plus OVA were subsequently exposed to OVA. CONCLUSIONS: Alternaria, but not Candida, is a potent catalyst for Th2-like acquired immunity to bystander antigens. The ability of ubiquitous fungi to enhance airway immune response to bystander antigens may play an important role in mounting an allergic response to aeroallergen.

Discrepancy between cytokine production from peripheral blood mononuclear cells and nasal secretions among infants with acute bronchiolitis

Many studies have measured cytokine production derived from peripheral blood mononuclear cells (PBMCs) to evaluate the immune response in acute bronchiolitis (AB), but no previous reports have examined the association between PBMC release of cytokines and concomitant airway immune response. To determine whether interferon-gamma (IFN-gamma), interleukin 4 (IL-4), and IL-10 levels from PBMCs are associated with concurrent cytokine release in the airways of infants with AB. Infants with acute viral-associated first episode of wheezing who required hospitalization between May and September 2002 were recruited. Nasopharyngeal aspirates (NPAs) and PBMC samples were collected simultaneously. The concentrations of IFN-gamma, IL-4, and IL-10 in NPA and PBMC supernatants were determined by enzyme-linked immunosorbent assay. Twenty infants with AB were enrolled in the study of whom 17 (85%) had positive NPA immunofluorescence results for viral detection and respiratory syncytial virus. Median total cell count and viability from NPA samples were 2.2 x 10(6) cells/mL (SD, 1.7 cells/mL) and 92% (SD, 6.0%), respectively. There was a significant correlation between IL-4 levels from NPA and PBMC samples (r = 0.5, P = .02); however, we did not find an association between IFN-gamma and IL-10 levels. Cytokines produced by in vitro PBMCs may not necessarily reflect the concurrent cytokine pattern production at the mucosal surface in the respiratory tract of infants with AB. Further studies are required to determine whether peripheral blood is a reliable sample for airway inflammation evaluation and to explain the discrepancies of cytokine productions found in this study.

Relationship between cutaneous allergen response and airway allergen-induced eosinophilia.

Determinants of changes in airway caliber after allergen challenge include nonallergic airway responsiveness, immune response and dose of allergen given. However, determinants of the airway inflammatory response to allergens remain to be determined. To assess the relationship between skin reactivity to airborne allergens and lower airway eosinophilic response to allergen exposure in asthma and allergic rhinitis. Forty-two subjects with mild allergic asthma (mean age 24 years) and 14 nonasthmatic subjects with allergic rhinitis (mean age 25 years) had allergen skin prick tests and titration with the allergen chosen for subsequent challenge. On a second visit, 31 asthmatic subjects had a conventional challenge while 11 asthmatic subjects and all rhinitic subjects had a low-dose allergen challenge over four subsequent days. Induced sputum samples were obtained at 6 and 24 h after the conventional challenge and at days 2 and 4 of the low-dose challenge. In the asthmatic group, there was a weak correlation between wheal diameter induced by the concentration used for challenge and increase in eosinophils 6 h postconventional challenge (r = 0.372, P = 0.05), but no correlation was observed following the low-dose challenge. Rhinitic subjects showed a correlation between wheal diameter with the allergen dose used for bronchoprovocation and increase in eosinophils at day 2 of low dose (r = 0.608, P = 0.02). This study suggests that immediate immune responsiveness to allergen, assessed by the magnitude of the skin response, is a significant determinant of allergen-induced airway eosinophilia and can help to predict the airway inflammatory response.

Airway epithelial cells release MIP-3alpha/CCL20 in response to cytokines and ambient particulate matter.

The initiation and maintenance of airway immune responses in Th2 type allergic diseases such as asthma are dependent on the specific activation of local airway dendritic cells (DCs). The cytokine microenvironment, produced by local cells, influences the recruitment of specific subsets of immature DCs and their subsequent maturation. In the airway, DCs reside in close proximity to airway epithelial cells (AECs). We examined the ability of primary culture human bronchial epithelial cells (HBECs) to synthesize and secrete the recently described CC-chemokine, MIP-3alpha/CCL20. MIP-3alpha/CCL20 is the unique chemokine ligand for CCR6, a receptor with a restricted distribution. MIP-3alpha/CCL20 induces selective migration of DCs because CCR6 is expressed on some immature DCs but not on CD14+ DC precursors or mature DCs. HBECs were stimulated with pro-inflammatory cytokines tumor necrosis factor-alpha and interleukin (IL)-1beta or, because of their critical role in allergic diseases, IL-4 and IL-13. Cells were also exposed to small size-fractions of ambient particulate matter. Each of these stimuli induced MIP-3alpha/CCL20 gene and protein expression. Moreover, these agents upregulated mitogen-activated protein kinase pathways in HBECs. Inhibition of the ERK1/2 pathway or p38 reduced cytokine-induced MIP-3alpha/CCL20 expression. These data suggest a mechanism by which AEC may facilitate recruitment of DC subsets to the airway.

Lymphocyte homing to bronchus-associated lymphoid tissue (BALT) is mediated by L-selectin/PNAd, alpha4beta1 integrin/VCAM-1, and LFA-1 adhesion pathways.

Bronchus-associated lymphoid tissue (BALT) participates in airway immune responses. However, little is known about the lymphocyte–endothelial adhesion cascades that recruit lymphocytes from blood into BALT. We show that high endothelial venules (HEVs) in BALT express substantial levels of VCAM-1, in marked contrast to HEVs in other secondary lymphoid tissues. BALT HEVs also express the L-selectin ligand PNAd. Anti–L-selectin, anti-PNAd, and anti–LFA-1 mAbs almost completely block the homing of B and T lymphocytes into BALT, whereas anti–α4 integrin and anti–VCAM-1 mAbs inhibit homing by nearly 40%. α4β7 integrin and MAdCAM-1 are not involved. Importantly, we found that mAbs against α4 integrin and VCAM-1 significantly block the migration of total T cells (80% memory phenotype) but not naive T and B cells to BALT. These results suggest that an adhesion cascade, which includes L-selectin/PNAd, α4β1 integrin/VCAM-1, and LFA-1, targets specific lymphocyte subsets to BALT. This high level of involvement of α4β1 integrin/VCAM-1 is unique among secondary lymphoid tissues, and may help unify lymphocyte migration pathways and immune responses in BALT and other bronchopulmonary tissues.

The IL-1 receptor 1 is critical for Th2 cell type airway immune responses in a mild but not in a more severe asthma model.

IL-1 alpha and IL-1 beta are potent pro-inflammatory cytokines that regulate many physiological systems by binding and signaling to the same receptor termed IL-1 receptor type 1 (IL-1R1). We have investigated the role of IL-1 for pulmonary immune responses in models of allergic asthma using IL-1R1-deficient (IL-1R1(-/-)) mice. In a model of mild asthma, based on repeated sensitization of mice with low doses of ovalbumin in the absence of any adjuvant and multiple intranasal challenges, the pulmonary eosinophilic inflammation and goblet cell hyperplasia were strongly reduced in IL-1R1(-/-) as compared to control BALB/c mice. Moreover, priming of CD4(+) T cells in bronchial lymph nodes and their recruitment to the lung was affected in IL-1R1(-/-) mice associated with impaired antibody responses including IgG, IgE, and IgA. In contrast, sensitization of mice in the presence of alum adjuvant, a more severe asthma model, rendered the IL-1 pathway dispensable for the development of pulmonary allergic Th2 responses, as eosinophilic inflammation, antibody responses, and CD4(+) T cell priming in lymph nodes were comparable between IL-1R1(-/-) and wild-type mice. These results suggest a critical role of IL-1/IL-1R1 for development of allergic Th2 responses, but its requirement can be overcome by using alum as adjuvant for sensitization.

Effect of Inhaled Ultrafine Carbon Particles on the Allergic Airway Response in Ragweed-Sensitized Dogs

Episodic increases in air pollution have been associated with the exacerbation of asthma symptoms. Ultrafine particles are a component of air pollution and may be involved in causing the adverse health effects associated with high air pollution. We evaluated the effects of ultrafine particle inhalation on immune and airway responses in a beagle dog model of allergic asthma. Six allergic (ragweed sensitive) and six nonallergic dogs were exposed to ultrafine carbon particles (232.3 ± 2.5 µg/m 3, 35.2 ± 0.3 nm) for 1 h, followed by a challenge with vehicle (water) as a negative control. Airway resistance was measured during particle exposure and after vehicle challenge. Immune responses 3 days before and after (1 h and 1, 4, 7, and 11 days) particle exposure were assessed by measuring total immunoglobulin E (IgE) and ragweed-specific IgE and IgG in serum and bronchoalveolar lavage fluid (BALF), and cell differentials in BALF. Each dog was exposed a second time to ultrafine carbon particles (251.4 ± 5.3 µg/m 3, 34.9 ± 0.5 nm) for 1 h followed by a challenge with ragweed and the same measurements. Airway resistance did not change during particle exposure in any of the dogs, and ragweed-induced airway reactivity was not altered by particle exposure. Total and ragweed-specific serum IgE and total IgE in BALF were higher in allergic dogs at all time points. Particle exposure did not affect antibody levels in serum or BALF in allergic dogs. Nonallergic dogs developed specific IgG in response to multiple inhalation exposures to ragweed, but this was not associated with particle exposure. Neutrophils were elevated in BALF for all groups 1 day after particle exposure. In conclusion, despite the induction of low level inflammation in the lungs of allergic and nonallergic dogs, exposure to ultrafine carbon particles did not alter airway reactivity or immune responses.