Roger S. Thrall

Suppression of immune complex vasculitis in rats by prostaglandin.

Immune complex-induced vascular damage can be markedly suppressed by treatment of rats with either prostaglandin (PG)E1 or its stable derivative, 15-(S)-15-methyl PGE1, but not with PGF2 alpha. In addition, PGD2 and PGE2 also show suppressive effects. The PGE1 derivative is considerably more effective than PGE1 and shows potent anti-inflammatory activity even after oral administration. Suppression of the vasculitis reaction is reflected by a greatly diminished increase in vasopermeability, indicating little or no vascular damage. In suppressed animals, the infiltration of neutrophils is greatly reduced, and those leukocytes that have appeared at tissue sites fail to show phagocytic uptake of immune complexes. In suppressed animals, the skin sites nevertheless show deposits of immune complexes and C3 fixation in vascular walls. Neutrophils harvested from the blood of rats treated with PGE1 show depressed responsiveness in chemotaxis and in enzyme secretion after incubation with chemotactic peptide. These studies indicate that certain PG have potent anti-inflammatory activity, which may be related to their effects on leukocytes.

Shifts in Lung Lymphocyte Profiles Correlate with the Sequential Development of Acute Allergic and Chronic Tolerant Stages in a Murine Asthma Model

T lymphocytes have a central regulatory role in the pathogenesis of asthma. We delineated the participation of lymphocytes in the acute allergic and chronic tolerant stages of a murine model of asthma by characterizing the various subsets of lymphocytes in bronchoalveolar lavage and lung tissue associated with these responses. Acute (10-day) aerosol challenge of immunized C57BL/6J mice with ovalbumin resulted in airway eosinophilia, histological evidence of peribronchial and perivascular airway inflammation, clusters of B cells and TCRgammadelta cells in lung tissue, increased serum IgE levels, and airway hyperresponsiveness to methacholine. In mice subjected to chronic (6-week) aerosol challenge with ovalbumin, airway inflammation and serum IgE levels were significantly attenuated and airway hyperresponsiveness was absent. The marked increases in lung B and T cell populations seen in the acute stage were also significantly reduced in the chronic stage of this model. Thus, acute ovalbumin challenge resulted in airway sensitization characteristic of asthma, whereas chronic ovalbumin challenge elicited a suppressed or tolerant state. The transition from antigenic sensitization to tolerance was accompanied by shifts in lymphocyte profiles in the lung and bronchoalveolar lavage fluid.

Regulatory Role of B Cells in a Murine Model of Allergic Airway Disease

Mice sensitized to OVA and subjected to acute OVA aerosol exposures develop allergic airway disease (AAD). However, chronic continuous Ag exposure results in resolution of AAD and the development of local inhalational tolerance (LIT). Because we have previously observed the persistence of B cells in the bronchoalveolar lavage (BAL) and hilar lymph nodes (HLN) at the resolution stage of this model, we investigated the role of B cells in the modulation of AAD. Although B cell-deficient mice developed LIT, adoptive transfer of HLN B cells from LIT mice to OVA-sensitized recipients resulted in attenuated AAD following subsequent OVA aerosol exposure, as determined by reduced BAL leukocytosis and eosinophilia, decreased tissue inflammation, and absent methacholine hyper-responsiveness. In similar adoptive transfer studies, HLN B cells from AAD mice were without effect. The protection transferred by LIT HLN B cells was Ag specific and was associated with accumulation of Foxp3+ T regulatory cells regionally in BAL and HLN, but not systemically in the spleen. Fluorescent labeling of LIT HLN B cells before adoptive transfer demonstrated that these cells had the capacity to migrate to local inflammatory sites. In vitro assessment demonstrated that the LIT HLN B cells exerted this regulatory effect via TGF-β induced conversion of CD4+CD25− T effector cells into functionally suppressive CD4+CD25+Foxp3+ T regulatory cells. These findings illustrated a novel regulatory role for regional B cells in AAD and suggested a possible contributory role of B cells, along with other cell types, in the establishment of LIT.

Chronic inhaled ovalbumin exposure induces antigen-dependent but not antigen-specific inhalational tolerance in a murine model of allergic airway disease.

Sensitized mice acutely challenged with inhaled ovalbumin (OVA) develop allergic airway inflammation, characterized by OVA-specific IgE production, airway eosinophilia, increased pulmonary B and T lymphocytes, and airway hyperreactivity. In this study, a chronic exposure model was developed and two distinct patterns of response were observed. Discontinuous inhalational exposure to OVA (6 weeks) produced airway inflammation and hyperreactivity that were similar to acute (10 days) responses. Continuous inhalational exposure to OVA (6 or 11 weeks) resulted in attenuation of airway eosinophilia and hyperresponsiveness without reduction of OVA-specific IgE and IgG(1) levels. The inhibition of airway inflammation was dependent on continuous exposure to antigen, because continuously exposed mice with attenuated inflammatory responses redeveloped allergic airway disease if the OVA aerosols were interrupted and then restarted (11-week-discontinuous). Inhalational tolerance induced by continuous OVA exposure demonstrated bystander suppression of cockroach allergen-mediated airway eosinophilia. These findings may be attributed to changes in production of the anti-inflammatory cytokine interleukin-10 during continuous OVA aerosol exposure. The symptomatic and asymptomatic allergic responses in human asthmatics could be explained by similar variable or discontinuous exposures to aeroantigens.

Regulatory B cells from hilar lymph nodes of tolerant mice in a murine model of allergic airway disease are CD5+, express TGF-β, and co-localize with CD4+Foxp3+ T cells.

In a biphasic, ovalbumin (OVA)-induced murine asthma model where allergic airway disease is followed by resolution and the development of local inhalational tolerance (LIT), transforming growth factor (TGF)-β-expressing CD5+ B cells were selectively expanded locally in hilar lymph nodes (HLN) of LIT mice. LIT HLN CD5+ B cells, but not LIT HLN CD5– B cells, induced expression of Foxp3 in CD4+CD25– T cells in vitro. These CD5+ regulatory B cells (Breg) and CD4+Foxp3+ T cells demonstrated similar increases in expression of chemokine receptors (CXCR4 and CXCR5) and co-localized in HLN B cell zones of LIT mice. The adoptive transfer of LIT HLN CD5+ B cells, but not LIT HLN CD5– B cells, increased the number of CD4+Foxp3+ T cells in the lung and inhibited airway eosinophilia in this OVA model. Thus, Breg in HLNs of LIT mice reside in a CD5+ TGF-β-producing subpopulation and co-localize with CD4+Foxp3+ T cells.

Murine Cytomegalovirus Infection Alters Th1/Th2 Cytokine Expression, Decreases Airway Eosinophilia, and Enhances Mucus Production in Allergic Airway Disease

Concomitant infection of murine CMV (MCMV), an opportunistic respiratory pathogen, altered Th1/Th2 cytokine expression, decreased bronchoalveolar lavage (BAL) fluid eosinophilia, and increased mucus production in a murine model of OVA-induced allergic airway disease. Although no change in the total number of leukocytes infiltrating the lung was observed between challenged and MCMV/challenged mice, the cellular profile differed dramatically. After 10 days of OVA-aerosol challenge, eosinophils comprised 64% of the total leukocyte population in BAL fluid from challenged mice compared with 11% in MCMV/challenged mice. Lymphocytes increased from 11% in challenged mice to 30% in MCMV/challenged mice, and this increase corresponded with an increase in the ratio of CD8+ to CD4+TCRαβ lymphocytes. The decline in BAL fluid eosinophilia was associated with a change in local Th1/Th2 cytokine profiles. Enhanced levels of IL-4, IL-5, IL-10, and IL-13 were detected in lung tissue from challenged mice by RNase protection assays. In contrast, MCMV/challenged mice transiently expressed elevated levels of IFN-γ and IL-10 mRNAs, as well as decreased levels of IL-4, IL-5, and IL-13 mRNAs. Elevated levels of IFN-γ and reduced levels of IL-5 were also demonstrated in BAL fluid from MCMV/challenged mice. Histological evaluation of lung sections revealed extensive mucus plugging and epithelial cell hypertrophy/hyperplasia only in MCMV/challenged mice. Interestingly, the development of airway hyperresponsiveness was observed in challenged mice, not MCMV/challenged mice. Thus, MCMV infection can modulate allergic airway inflammation, and these findings suggest that enhanced mucus production may occur independently of BAL fluid eosinophilia.

Accumulation of regulatory T cells in local draining lymph nodes of the lung correlates with spontaneous resolution of chronic asthma in a murine model.

Background: Mice sensitized to ovalbumin develop allergic airway disease (AAD) with short-term aerosol challenge; however, airway inflammation resolves with long-term aerosol challenge, referred to as local inhalational tolerance (LIT). Methods: We sought to determine if resolution of airway inflammation correlated with increases in lymphocyte subsets in local lung compartments, including putative regulatory T cells. Results: At the AAD stage, total numbers of T and B lymphocytes in bronchoalveolar lavage (BAL) were significantly increased above controls; however, at LIT, T and B lymphocytes were significantly reduced compared to AAD. In the lung tissue, the only alteration was a significant increase in CD4+ CD25+ T cells at AAD. In the hilar lymph node (HLN), CD4+ and CD4+ CD25+ T cells were significantly increased at AAD and LIT. In addition, CD8+ T cells were significantly elevated in the HLN at LIT, and CD19+ B cells were significantly increased at AAD. Adoptive transfer of HLN lymphocytes to lymphopenic mice confirmed that AAD lymphocytes could induce airway inflammation in response to aerosol challenge, whereas LIT lymphocytes were unable to do so. Depletion of CD4+ CD25+ T cells in vivo resulted in exacerbation of inflammation at AAD and LIT. CD4+ CD25+ T cells in the HLN also displayed suppressive activity in vitro. Additionally, T cells expressing Foxp3 were increased in the BAL and HLN during LIT. Conclusions: These results indicate that lymphocytes with regulatory functions are increased and sustained in local lung compartments at LIT and that their appearance correlates with the resolution of lung inflammation.

Maternal Transmission of Resistance to Development of Allergic Airway Disease

Parental phenotype is known to influence the inheritance of atopic diseases, such as allergic asthma, with a maternal history being a more significant risk factor for progeny than paternal history. We hypothesized that recall Th1- or Th2-type immune responses during pregnancy would result in transfer of maternal factors that would differentially impact development of immune responsiveness in offspring. Following weaning, susceptibility and severity of allergic airway disease (a murine model of human asthma) was evaluated in progeny, disease being elicited by immunization with OVA-Al(OH)3 and challenge with aerosolized OVA. We found that progeny of mothers with Th1-biased immunity to OVA subjected to recall aerosol challenge during pregnancy had reduced levels of Ag-specific IgE and airway eosinophilia compared with progeny of mothers with Th2-biased immunity to OVA or naive mothers. Interestingly, progeny of mothers with Th1-type immunity to a heterologous albumin, BSA, were not protected from developing OVA-induced allergic airway disease. These findings demonstrated that maternal transfer of protection from development of allergic airway disease to offspring in this model of maternal Th1-type immunity was Ag specific.

Oral Bromelain Attenuates Inflammation in an Ovalbumin-induced Murine Model of Asthma.

Bromelain, a widely used pineapple extract with cysteine protease activity, has been shown to have immunomodulatory effects in a variety of immune system models. The purpose of the present study was to determine the effects of orally administered bromelain in an ovalbumin (OVA)-induced murine model of acute allergic airway disease (AAD). To establish AAD, female C57BL/6J mice were sensitized with intraperitoneal (i.p.) OVA/alum and then challenged with OVA aerosols for 3 days. Mice were gavaged with either (phosphate buffered saline)PBS or 200 mg/kg bromelain in PBS, twice daily for four consecutive days, beginning 1 day prior to OVA aerosol challenge. Airway reactivity and methacholine sensitivity, bronchoalveolar lavage (BAL) cellular differential, Th2 cytokines IL-5 and IL-13, and lung histology were compared between treatment groups. Oral bromelain-treatment of AAD mice demonstrated therapeutic efficacy as evidenced by decreased methacholine sensitivity (P ≤ 0.01), reduction in BAL eosinophils (P ≤ 0.02) and IL-13 concentrations (P ≤ 0.04) as compared with PBS controls. In addition, oral bromelain significantly reduced BAL CD19+ B cells (P ≤ 0.0001) and CD8+ T cells (P ≤ 0.0001) in AAD mice when compared with controls. These results suggest that oral treatment with bromelain had a beneficial therapeutic effect in this murine model of asthma and bromelain may also be effective in human conditions.

Inhalation of Staphylococcus aureus Enterotoxin A Induces IFN-γ and CD8 T Cell-Dependent Airway and Interstitial Lung Pathology in Mice

Staphylococcus aureus, a primary source of bacterial superantigen (SAg), is known to colonize the human respiratory tract and has been implicated in airway inflammation. Studies have documented a role for SAgs in respiratory disorders, such as nasal polyps, chronic obstructive pulmonary disease, chronic rhinosinusitis, and asthma. However, cellular and molecular mediators involved in SAg-mediated pulmonary disease have not been clearly identified. In this study, we investigated the effect of intranasal staphylococcal enterotoxin A (SEA) exposure on murine lung. The pathological features in the lung resulting from SEA exposure had characteristics of both obstructive and restrictive pulmonary disorders. There was also an increase in bronchoalveolar lavage protein concentration and cellularity following SEA challenge. Massive CD8+Vβ3+ T cell accumulation observed in the lung was dependent on CD4 T cell help, both for recruitment and for IFN-γ synthesis. The primary source of IFN-γ synthesis was CD8 T cells, and depletion of these cells abrogated disease. IFN-γ deficiency also prevented SEA-mediated disease, and this was by enhancing early recruitment of neutrophils as detected in the bronchoalveolar lavage. Thus, IFN-γ appeared to selectively aid the recruitment of T cells to the lungs while preventing the neutrophil accumulation. Therefore, our results show that IFN-γ-producing CD8 T cells mediated pulmonary alveolitis and inflammation, which were dependent upon CD4 T cells for their recruitment to the lung.