Allergic Inflammation in Aspergillus fumigatus-Induced Fungal Asthma.

Although fungi are pervasive in many environments, few cause disease in humans. Of these, Aspergillus fumigatus is particularly well suited to be a pathogen of the human lung. Its physical and biological characteristics combine to provide an organism that can cause tremendous morbidity and high mortality if left unchecked. Luckily, that is rarely the case. However, repeated exposure to inhaled A. fumigatus spores often results in an immune response that carries significant immunopathology, exacerbating asthma and changing the structure of the lung with chronic impacts to pulmonary function. This review focuses on the current understanding of the mechanisms that are associated with fungal exposure, sensitization, and infection in asthmatics, as well as the function of various inflammatory cells associated with severe asthma with fungal sensitization.

The immune profile associated with acute allergic asthma accelerates clearance of influenza virus.

Asthma was the most common comorbidity in hospitalized patients during the 2009 influenza pandemic. For unknown reasons, hospitalized asthmatics had less severe outcomes and were less likely to die from pandemic influenza. Our data with primary human bronchial cells indicate that changes intrinsic to epithelial cells in asthma may protect against cytopathology induced by influenza virus. To further study influenza virus pathogenesis in allergic hosts, we aimed to develop and characterize murine models of asthma and influenza comorbidity to determine structural, physiological and immunological changes induced by influenza in the context of asthma. Aspergillus fumigatus-sensitized and -challenged C57BL/6 mice were infected with pandemic H1N1 influenza virus, either during peak allergic inflammation or during airway remodeling to gain insight into disease pathogenesis. Mice infected with the influenza virus during peak allergic inflammation did not lose body weight and cleared the virus rapidly. These mice exhibited high eosinophilia, preserved airway epithelial cell integrity, increased mucus, reduced interferon response and increased insulin-like growth factor-1. In contrast, weight loss and viral replication kinetics in the mice that were infected during the late airway remodeling phase were equivalent to flu-only controls. These mice had neutrophils in the airways, damaged airway epithelial cells, less mucus production, increased interferons and decreased insulin-like growth factor-1. The state of the allergic airways at the time of influenza virus infection alters host responses against the virus. These murine models of asthma and influenza comorbidity may improve our understanding of the epidemiology and pathogenesis of viral infections in humans with asthma.

Hyaluronan deposition and co-localization with inflammatory cells and collagen in a murine model of fungal allergic asthma.

OBJECTIVE: Allergic asthma is a chronic inflammatory disease of the airways characterized by excessive inflammation and remodeling of the extracellular matrix (ECM) and associated cells of the airway wall. Under inflammatory conditions, hyaluronan (HA), a major component of the ECM, undergoes dynamic changes, which may in turn affect the recruitment and activation of inflammatory cells leading to acute and chronic immunopathology of allergic asthma. METHODS: In the present study, we measured the changes in HA levels generated at sites of inflammation, and examined its effect on inflammatory responses and collagen deposition in an Aspergillus fumigatus murine inhalational model of allergic asthma. RESULTS: We found that HA levels are elevated in allergic animals and that the increase correlated with the influx of inflammatory cells 5 days after the second allergen challenge. This increase in HA levels appeared largely due to upregulation of hyaluronidase-1 (HYAL1) and hyaluronidase-2 (HYAL2). Furthermore, HA co-localizes with areas of new collagen synthesis and deposition. CONCLUSIONS: Overall, our findings contribute to the growing literature that focuses on the components of ECM as inflammatory mediators rather than mere structural support products. The evidence of HA localization in fungal allergic asthma provides the impetus to study HA more closely with allergic leukocytes in murine models. Further studies examining HA's role in mediating cellular responses may help to develop targets for treatment in patients with severe asthma due to fungal sensitization.

µ-chain-deficient mice possess B-1 cells and produce IgG and IgE, but not IgA, following systemic sensitization and inhalational challenge in a fungal asthma model.

Allergic bronchopulmonary aspergillosis is often difficult to treat and results in morbidity associated with chronic airway changes. This study assessed the requirement for B cells and their products in the allergic pulmonary phenotype in a murine model of fungal allergic asthma that mimics allergic bronchopulmonary aspergillosis. C57BL/6 and µMT mice (assumed to lack peripheral B cells) were sensitized with Aspergillus fumigatus extract and challenged with two inhalation exposures of live conidia to induce airway disease. Airway hyperresponsiveness after methacholine challenge, peribronchovascular inflammation, goblet cell metaplasia, and fibrotic remodeling of the airways was similar between µMT mice and their wild-type counterparts (C57BL/6). Surprisingly, even in the absence of the µ-chain, these µMT mice produced IgE and IgG Abs, although the Abs induced did not have specificity for A. fumigatus Ags. In contrast, IgA was not detected in either the lavage fluid or serum of µMT mice that had been exposed to A. fumigatus. Our findings also reveal the existence of CD19(+)CD9(+)IgD(+) B-1 cells in the lungs of the µMT animals. These data show the µMT mice to have a developmental pathway independent of the canonical µ-chain route that allows for their survival upon antigenic challenge with A. fumigatus conidia, although this pathway does not seem to allow for the normal development of Ag-specific repertoires. Additionally, this study shows that IgA is not required for either clearance or containment of A. fumigatus in the murine lung, as fungal outgrowth was not observed in the µMT animals after multiple inhalation exposures to live conidia.

An inhalation model of airway allergic response to inhalation of environmental Aspergillus fumigatus conidia in sensitized BALB/c mice.

Fungal exposure may elicit a number of pulmonary diseases in man, including allergic asthma. Fungal sensitization is linked to asthma severity, although the basis for this increased pathology remains ambiguous. To create conditions simulating environmental fungal allergen exposure in a human, nose-only inhalation delivery of Aspergillus fumigatus conidia was employed in mice previously sensitized to Aspergillus antigen extract. BALB/c mice were immunized with subcutaneous and intraperitoneal injections of soluble A. fumigatus extract in alum, which was followed by three intranasal inoculations of the same fungal antigens dissolved in saline to elicit global sensitization in a manner similar to other published models. The animals were then challenged with a 10-min inhaled dose of live conidia blown directly from the surface of a mature A. fumigatus culture. After a single challenge with inhaled A. fumigatus conidia, allergic pulmonary inflammation and airway hyperresponsiveness were significantly increased above that of either naïve animals or animals that had been sensitized to A. fumigatus antigens but not challenged with conidia. The architecture of the lung was changed by inhalation of conidia when compared to controls in that there were significant increases in epithelial thickness, goblet cell metaplasia, and peribronchial collagen deposition. Additionally, α-smooth muscle actin staining of histological sections showed visual evidence of increased peribronchial smooth muscle mass after fungal challenge. In summary, the delivery of live A. fumigatus conidia to the sensitized airways of BALB/c mice advances the study of the pulmonary response to fungi by providing a more natural route of exposure and, for the first time, demonstrates the consistent development of fibrosis and smooth muscle changes accompanying exposure to inhaled fungal conidia in a mouse model.

Chemokines and cytokines: axis and allies in asthma and allergy.

Allergic asthma can be precipitated by many factors. For the atopic person, fungus, pollen, dust mites, cockroach antigens, and diesel exhaust are all agents that may trigger an allergic attack. Cytokines and chemokines are integral mediators of fungal asthma. From the earliest time points, they recruit and activate the cells required for the clearance of fungus as well as being critical factors involved in the immunopathology of this disease. In the final analysis, it is clear that these mediators can act to the benefit or the detriment of the host.

The therapeutic potential in targeting CCR5 and CXCR4 receptors in infectious and allergic pulmonary disease.

Targeting chemokines and chemokine receptors in various acute and chronic pulmonary diseases remains a vibrant area of basic and clinical research despite major hurdles including cross-species barriers, toxicity, and redundancy. In this review, we draw upon our basic research with a murine model in which innate and acquired immunity are linked in the development and maintenance of chronic asthma due to Aspergillus fumigatus. Using intact and genetically altered mice, studies have also been undertaken to elucidate safe and effective therapeutic strategies that interrupt the initiation and amplification of inflammatory and immune events that follow the intrapulmonary introduction of Aspergillus into A. fumigatus-sensitized mice. These events include resident immune cell activation, immune and inflammatory cell recruitment to the airways, changes in lung physiology, and profound changes in the architecture of the airway due to the activation of lung resident cells. The expression of 2 major chemokine receptors, namely, CC chemokine receptor (CCR) 5 and CXC chemokine receptor (CXCR) 4, has been identified and their roles in innate and acquired immune events during fungal asthma have been explored. CCR5 and CXCR4 are best known for their roles in human immunodeficiency virus-1 (HIV-1) infection, but both are attractive targets in the context of overt inflammatory and remodeling responses in the lung. This avenue of research is markedly enhanced by the existence of numerous small molecule antagonists that are available to selectively target these receptors.

Therapeutic targeting of CCR1 attenuates established chronic fungal asthma in mice.

CC chemokine receptor 1 (CCR1) represents a promising target in chronic airway inflammation and remodeling due to fungus-associated allergic asthma. The present study addressed the therapeutic effect of a nonpeptide CCR1 antagonist, BX-471, in a model of chronic fungal asthma induced by Aspergillus fumigatus conidia. BX-471 treatment of isolated macrophages inhibited CCL22 and TNF-alpha and promoted IL-10 release. BX-471 also increased toll like receptor-9 (TLR9) and decreased TLR2 and TLR6 expression in these cells. When administered daily by intraperitoneal injection, from days 15 to 30 after the initiation of chronic fungal asthma, BX-471 (3, 10, or 30 mg kg(-1)) dose-dependently reduced airway inflammation, hyper-responsiveness, and remodeling at day 30 after conidia challenge. The maximal therapeutic effect was observed at the 10 mg kg(-1) dose. In summary, the therapeutic administration of BX-471 significantly attenuated experimental fungal asthma via its effects on both innate and adaptive immune processes.

The role of CC chemokine receptor 5 (CCR5) and RANTES/CCL5 during chronic fungal asthma in mice.

In the present study, we explored the role of CC chemokine receptor 5 (CCR5) in a murine model of chronic fungal asthma induced by an intrapulmonary challenge with Aspergillus fumigatus conidia (or spores). Airway hyperresponsiveness was significantly lower in A. fumigatus-sensitized mice lacking CCR5 (CCR5-/-) compared with similarly sensitized wild-type (CCR5+/+) control mice at days 2, 21, 30, and 40 after the conidia challenge. CCR5-/- mice exhibited significantly less peribronchial T-cell and eosinophil accumulation and airway-remodeling features, such as goblet cell hyperplasia and peribronchial fibrosis, compared with CCR5+/+ mice at these times after conidia. However, both groups of mice exhibited similar allergic airway disease at day 12 after the conidia challenge. In CCR5-/- mice at day 12, the allergic airway disease was associated with airway hyperresponsiveness, peribronchial allergic inflammation, and goblet cell hyperplasia. Immunoneutralization of RANTES/CCL5 in sensitized CCR5+/+ and CCR5-/- mice for 12 days after the conidia challenge significantly reduced the peribronchial inflammation and airway hyperresponsiveness in comparison with control wild-type and knockout mice at this time. These data demonstrate that functional CCR5 and RANTES/CCL5 are required for the persistence of chronic fungal asthma in mice.

Airway hyperresponsiveness, but not airway remodeling, is attenuated during chronic pulmonary allergic responses to Aspergillus in CCR4-/- mice.

The role of CC chemokine receptor 4 (CCR4) during the development and maintenance of Th2-type allergic airway disease is controversial. In this study, we examined the role of CCR4 in the chronic allergic airway response to live Aspergillus fumigatus spores, or conidia, in A. fumigatus-sensitized mice. After the conidia challenge, mice lacking CCR4 (CCR4-/- mice) exhibited significantly increased numbers of airway neutrophils and macrophages, and conidia were more rapidly eliminated from these mice compared with control CCR4 wild-type (CCR4+/+) mice. Significant airway hyperresponsiveness to intravenous methacholine was observed at day 3 in CCR4-/- mice, whereas at days 7 and 30, airway hyperresponsiveness was attenuated in these mice compared with control mice. A major reduction in peribronchial and airway eosinophilia was observed in CCR4-/- mice at all times after conidia challenge in contrast to CCR4+/+ mice. Further, whole lung levels of interleukin (IL) 4 and IL-5 were significantly increased in CCR4-/- mice at day 3, whereas these Th2 cytokines and IL-13 were significantly decreased at day 30 in CCR4-/- mice compared with their wild-type counterparts. Peribronchial fibrosis and goblet cell hyperplasia were similar in both groups of mice throughout the course of this model. In summary, CCR4 modulates both innate and acquired immune responses associated with chronic fungal asthma.

Mannose-binding lectin deficiency alters the development of fungal asthma: effects on airway response, inflammation, and cytokine profile.

Aspergillus fumigatus is a major fungal pathogen that may be fatal to immunocompromised individuals and causes airway hyperreactivity and remodeling in sensitized individuals. Herein, we examined the role of mannose-binding lectin (MBL), a complement-activating plasma protein, during pulmonary innate and allergic immune responses directed against A. fumigatus spores or conidia. Neither group of nonsensitized MBL-A-sufficient (MBL-A+/+) nor -deficient (MBL-A-/-) mice challenged with an intravenous or intratracheal (i.t.) bolus of A. fumigatus spores experienced fungus-induced mortality, but marked airway remodeling was observed in MBL-A-/- mice challenged i.t. with conidia. In a model of chronic fungal asthma, MBL-A+/+ and MBL-A-/- A. fumigatus-sensitized mice were examined at days 4 and 28 after an i.t. challenge with A. fumigatus conidia. Airway hyperresponsiveness in sensitized MBL-A-/- mice was significantly decreased at both times after conidia challenge compared with the sensitized MBL-A+/+ group. In the sensitized MBL-A-/- mice, whole lung T helper cell type 2 cytokine levels were significantly decreased at day 4 after conidia, and whole lung interferon-gamma levels were significantly increased at day 28 after conidia when compared with controls. However, histological evidence showed similar airway remodeling at day 28 after conidia (i.e., subepithelial fibrosis and goblet cell metaplasia) in the two groups of mice. Thus, these findings show that MBL-A is not required for mouse survival following exposure to A. fumigatus conidia, and this murine collectin isoform contributes to the development and maintenance of airway hyperresponsiveness but not chronic airway remodeling during chronic fungal asthma.

Hyaluronan fragments as mediators of inflammation in allergic pulmonary disease.

Asthma is frequently caused and/or exacerbated by sensitization to allergens, which are ubiquitous in many indoor and outdoor environments. Severe asthma is characterized by airway hyperresponsiveness and bronchial constriction in response to an inhaled allergen, leading to a disease course that is often very difficult to treat with standard asthma therapies. As a result of interactions among inflammatory cells, structural cells, and the intercellular matrix of the allergic lung, patients with sensitization to allergens may experience a greater degree of tissue injury followed by airway wall remodeling and progressive, accumulated pulmonary dysfunction as part of the disease sequela. In addition, turnover of extracellular matrix (ECM) components is a hallmark of tissue injury and repair. This review focuses on the role of the glycosaminoglycan hyaluronan (HA), a component of the ECM, in pulmonary injury and repair with an emphasis on allergic asthma. Both the synthesis and degradation of the ECM are critical contributors to tissue repair and remodeling. Fragmented HA accumulates during tissue injury and functions in ways distinct from the larger native polymer. There is gathering evidence that HA degradation products are active participants in stimulating the expression of inflammatory genes in a variety of immune cells at the injury site. In this review, we will consider recent advances in the understanding of the mechanisms that are associated with HA accumulation and inflammatory cell recruitment in the asthmatic lung.

B lymphocytes regulate airway granulocytic inflammation and cytokine production in a murine model of fungal allergic asthma.

Sensitization to fungi often leads to a severe form of asthma that is particularly difficult to manage clinically, resulting in increased morbidity and hospitalizations in these patients. Although B lymphocytes might exacerbate asthma symptoms through the production of IgE, these cells might also be important in the protective response against inhaled fungi. Through cytokine release and T-cell interactions, these lymphocytes might also influence the development and maintenance of airway wall fibrosis. J(H)(-/-) mice lack the JH gene for the heavy chain component of antibodies, which is critical for B-cell function and survival. These animals have facilitated the elucidation of the role of B lymphocytes in a number of immune responses; however, J(H)(-/-) mice have not been used to study fungal allergy. In this study, we examined the role of B lymphocytes using an Aspergillus fumigatus murine fungal aeroallergen model that mimics human airway disease that is triggered by environmental fungal exposure. We compared disease progression in sensitized wild-type BALB/c and J(H)(-/-) mice that were exposed to repeated fungal exposure and found no differences in airway hyperresponsiveness, overall pulmonary inflammation or collagen deposition around the large airways. However, the levels of the Th2-type cytokines IL-4 and IL-13 were significantly attenuated in the airways of J(H)(-/-) mice relative to the BALB/c controls. By contrast, levels of the inflammatory cytokines IL-17A and IL-6 were significantly elevated in the J(H)(-/-) animals, and there was significantly more robust airway eosinophilia and neutrophilia than in control animals. Taken together, these findings demonstrate that B lymphocytes help to regulate granulocytic responses to fungal exposure in the pulmonary compartment.

Hyaluronan stimulates ex vivo B lymphocyte chemotaxis and cytokine production in a murine model of fungal allergic asthma.

Allergic asthma is a chronic inflammatory disease of the airways characterized by excessive eosinophilic and lymphocytic inflammation with associated changes in the extracellular matrix (ECM) resulting in airway wall remodeling. Hyaluronan (HA) is a nonsulfated glycosaminoglycan ECM component that functions as a structural cushion in its high molecular mass (HMM) but has been implicated in metastasis and other disease processes when it is degraded to smaller fragments. However, relatively little is known about the role HA in mediating inflammatory responses in allergy and asthma. In the present study, we used a murine Aspergillus fumigatus inhalational model to mimic human disease. After observing in vivo that a robust B cell recruitment followed a massive eosinophilic egress to the lumen of the allergic lung and corresponded with the detection of low molecular mass HA (LMM HA), we examined the effect of HA on B cell chemotaxis and cytokine production in the ex vivo studies. We found that LMM HA functioned through a CD44-mediated mechanism to elicit chemotaxis of B lymphocytes, while high molecular mass HA (HMM HA) had little effect. LMM HA, but not HMM HA, also elicited the production of IL-10 and TGF-ß1 in these cells. Taken together, these findings demonstrate a critical role for ECM components in mediating leukocyte migration and function which are critical to the maintenance of allergic inflammatory responses.

Cytokines and chemokines in allergic bronchopulmonary aspergillosis (ABPA) and experimental Aspergillus-induced allergic airway or asthmatic disease.

Allergic bronchopulmonary aspergillosis (ABPA) is a devastating clinical disease that results from an aggressive pulmonary allergic response to the antigens released by colonizing Aspergillus fumigatus (A. fumigatus) in the respiratory system. Many of the allergic features of clinical ABPA have been reproduced in murine models, thereby facilitating a detailed analysis of the inflammatory and immune events that surround the initiation and maintenance of this disease. Herein, we describe the involvement of cytokines and chemokines in murine allergic pulmonary disease elicited by A. fumigatus antigens and spores (or conidia). More importantly, data derived from murine models of Aspergillus-induced allergic airway disease or asthma also suggest that the specific targeting of cytokines and/or chemokines may provide a novel therapeutic strategy in the treatment of clinical ABPA.

An inhalation model of allergic fungal asthma: Aspergillus fumigatus-induced inflammation and remodeling in allergic airway disease.

The ability to accurately mimic normal processes for sensitization and allergen challenge in an experimental animal model are useful in that they allow researchers to critically manipulate the complex interactions of multiple cell types. In the context of the allergic lung, multiple cell types form complex cellular networks and function to regulate a variety of temporal and spatial changes. Mouse models of allergic airway disease have proven to be highly useful for dissecting these complex interactions, particularly in addressing remodeling of the allergic airway in chronic asthma. Until we can better represent the normal processes that initiate and perpetuate asthma, our understanding of the mechanisms of tissue injury leading to chronic remodeling of the airways and effective therapeutic strategies to treat this disease will remain limited. It was with this goal in mind that we set about devising an inhalational model of Aspergillus fumigatus-induced fungal asthma in a murine experimental system.

The impact of Aspergillus fumigatus viability and sensitization to its allergens on the murine allergic asthma phenotype.

Aspergillus fumigatus is a ubiquitously present respiratory pathogen. The outcome of a pulmonary disease may vary significantly with fungal viability and host immune status. Our objective in this study was (1) to assess the ability of inhaled irradiation-killed or live A. fumigatus spores to induce allergic pulmonary disease and (2) to assess the extent to which inhaled dead or live A. fumigatus spores influence pulmonary symptoms in a previously established allergic state. Our newly developed fungal delivery apparatus allowed us to recapitulate human exposure through repeated inhalation of dry fungal spores in an animal model. We found that live A. fumigatus spore inhalation led to a significantly increased humoral response, pulmonary inflammation, and airway remodeling in naïve mice and is more likely to induce allergic asthma symptoms than the dead spores. In contrast, in allergic mice, inhalation of dead and live conidia recruited neutrophils and induced goblet cell metaplasia. This data suggests that asthma symptoms might be exacerbated by the inhalation of live or dead spores in individuals with established allergy to fungal antigens, although the extent of symptoms was less with dead spores. These results are likely to be important while considering fungal exposure assessment methods and for making informed therapeutic decisions for mold-associated diseases.

Eosinophils in fungus-associated allergic pulmonary disease.

Asthma is frequently caused and/or exacerbated by sensitization to fungal allergens, which are ubiquitous in many indoor and outdoor environments. Severe asthma with fungal sensitization is characterized by airway hyperresponsiveness and bronchial constriction in response to an inhaled allergen that is worsened by environmental exposure to airborne fungi and which leads to a disease course that is often very difficult to treat with standard asthma therapies. As a result of complex interactions among inflammatory cells, structural cells, and the intercellular matrix of the allergic lung, patients with sensitization to fungal allergens may experience a greater degree of airway wall remodeling and progressive, accumulated pulmonary dysfunction as part of the disease sequela. From their development in the bone marrow to their recruitment to the lung via chemokine and cytokine networks, eosinophils form an important component of the inflammatory milieu that is associated with this syndrome. Eosinophils are recognized as complex multi-factorial leukocytes with diverse functions in the context of allergic fungal asthma. In this review, we will consider recent advances in our understanding of the molecular mechanisms that are associated with eosinophil development and migration to the allergic lung in response to fungal inhalation, along with the eosinophil's function in the immune response to and the immunopathology attributed to fungus-associated allergic pulmonary disease.

Characterization of CD19(+)CD23(+)B2 lymphocytes in the allergic airways of BALB/c mice in response to the inhalation of Aspergillus fumigatus conidia.

Fungal sensitization in patients with asthma often indicates an unusual disease course in which traditional asthma treatments have little effect and in which morbidity is particularly severe. Airway hyperresponsiveness (AHR), inflammatory infiltrates, smooth muscle hyperplasia, and irreversible fibrotic remodeling of the bronchial architecture are features of allergic fungal asthma. The systemic production of IgE has long been associated with the immunopathogenesis of allergic asthma; however, the role of B lymphocytes and their products in the response to fungal allergens remains unclear. In the present study, we hypothesize that B lymphocytes are recruited to the allergic lung to impact the allergic response. Using a murine fungal aeroallergen model to mimic the human syndrome, we characterized the B cell population in the lung after fungal challenge and found that CD19(+)CD23(+) B2 lymphocyte numbers are increased in the allergic lung in a dynamic process. IgA, IgG(2a), and IgE were prominent in the serum and bronchoalveolar lavage fluid of allergic animals. It was evident that a tissue-centric production of these antibodies was possible. IgA-, IgG-, and IgE-producing cells from the allergic lung were identified by flow cytometry and immunohistochemistry. This study shows for the first time that CD19(+)CD23(+) B2 lymphocyte numbers change in the lung in a dynamic process after inhalation of fungal conidia and their increase has a significant impact on the Ab production in the pulmonary compartment in the context of fungal allergy.

The absence of VPAC2 leads to aberrant antibody production in Aspergillus fumigatus sensitized and challenged mice.

Vasoactive intestinal peptide (VIP) facilitates a "pro-allergy" phenotype when signaling through its G protein-coupled receptor, VPAC(2). We have shown that VPAC(2) knock-out (KO) mice developed an allergic phenotype marked by eosinophilia and elevated serum IgE. Therefore, we hypothesized that the humoral response to allergen challenge in these mice was T(H)2 dominant similar to wild-type (WT) C57BL/6 mice. Antibody responses in WT and KO mice were measured after Aspergillus fumigatus conidia inhalation. In contrast to previous reports, basal levels of serum IgG(2a) and IgA were significantly higher in naïve VPAC(2) KO animals. Antibody availability in the serum as well as the bronchoalveolar lavage fluid after fungal challenge was dominated by the pro-inflammatory isotype IgG(2a) and the mucosal isotype, IgA. IgA localizing cells dominated in the peribronchovascular areas of allergic KO mice while IgE immune complexes were found in WT allergic lungs. This research shows for the first time that VPAC(2) has a significant effect on antibody regulation, in the context of allergy.