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

Abstract

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 TCR␥␦ 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. Asthma is the most common chronic illness in developed countries. Our current understanding of the pathophysiology of allergic asthma is that it occurs from a breakdown of the normal tolerance to inhaled antigens, as a result of complex interactions between host and environmental factors. Emerging evidence suggests that the development of clinical sensitivity versus normal tolerance to inhaled antigens involves the establishment of a dominant population of CD4 ϩ T lymphocytes that are either classified as Th2-like (sensitization) or Th1-like (tolerance).1 Th2 responses are characterized by secretion of the cytokines interleukin (IL)-4 and IL-13, which induce the production of IgE by B cells, 2-5 and IL-5, which regulates the growth, differentiation, and activation of eosinophils.6 Conversely, Th1 responses are characterized by secretion of IL-2, tumor necrosis factor (TNF)-␤, and interferon (IFN)-␥. IFN-␥ has been shown to stimulate low-level IgG production and to potently inhibit IL-4-mediated IgE responses both in vivo and in vitro.7 The mechanisms that control CD4 ϩ T lymphocyte polarization into either Th1 or Th2 phenotypes are incompletely understood but appear to involve genetic predispositions, local factors such as existing cytokine concentrations and inflammation, and antigenic factors such as the potency, dose, and duration of exposure of the eliciting antigen. In susceptible individuals, antigen sensitization results in specific local and systemic IgE production and airway eosinophilia, which in turn induce the airway inflammation, airway hyperresponsiveness, and reversible airway obstruction characteristic of asthma.The factors influencing antigen sensitization or tolerance can be better studied in mice, given their well defined...

Chronic Inhaled Ovalbumin Exposure Induces Antigen-Dependent but Not Antigen-Specific Inhalational Tolerance in a Murine Model of Allergic Airway Disease

“…11 Briefly, they were given three weekly intraperitoneal injections of a suspension containing 25 g of OVA (grade V; Sigma Chemical Co., St. Louis, MO) and 2 mg of aluminum hydroxide (alum) in 0.5 ml of saline. One week after the last injection the mice were exposed to 1% aerosolized OVA according to one of five protocols: 1) wild-type and TCR␦ Ϫ/Ϫ mice exposed to OVA 1 hour/day for 10 days (acute); 2) wild-type and TCR␦ Ϫ/Ϫ mice exposed to OVA 1 hour/day for 10 days followed by 1 hour/day, 5 days/week for 4 weeks and then 1 hour/day for 10 days (6-week-continuous); 3) wild-type and TCR␦ Ϫ/Ϫ mice exposed to OVA 1 hour/day for 10 days followed by no aerosol exposures for 4 weeks and then aerosol exposures of 1 hour/day for 10 days (6-week-discontinuous); 4) wildtype mice treated according to the continuous protocol above, then exposed to aerosolized OVA 5 days/week for an additional 4-week period, followed by 1 hour/day for 7 to 10 days (11-week-continuous); and 5) wild-type mice treated according to the continuous protocol above, then had OVA aerosols stopped and then resumed 4 weeks later at 1 hour/day for 7 to 10 days (11-week-discontinuous).…”

“…As previously reported, this aerosol system generated OVA particles of 1.4-mol/L mass median aerodynamic diameter and 1.6-m geometric standard deviations. 11 Exposure to the 1% OVA aerosol for 1 hour resulted in an average inhaled OVA dose of 80 g/mouse. 11 Twentyfour hours after the final aerosol exposure, the mice were sacrificed by ketamine/xylazine overdose and exsanguination, and analyses of bronchoalveolar lavage (BAL), lung tissue, and blood samples were performed.…”

“…We have recently demonstrated that C57BL/6J mice undergo a biphasic response to aerosolized ovalbumin (OVA) exposure. 11 After initial immunization and daily aerosol challenge with OVA for 3 to 10 days, mice develop allergic airway disease, characterized by antigen-specific IgE production, airway eosinophilia, increased pulmonary B and T lymphocytes, and airway hyperresponsiveness. In contrast, 6-weekcontinuous daily aerosol challenge with OVA results in attenuation of these allergic responses.…”

CCL25 induces α4β7 integrin‐dependent migration of IL‐17+γδ T lymphocytes during an allergic reaction

“…γδ T cells have been shown to migrate into the airways during allergic inflammation highly controlled by a chemotactic gradient of chemokines produced in tissue [5,[7][8][9][10][11]. We have previously demonstrated that allergen-induced γδ T-cell accumulation is * These authors contributed equally to this work.…”

“…This unique subset of lymphocytes can provide rapid tissue-specific immune responses, without the requirement of antiCorrespondence: Dr. Carmen Penido e-mail: cpenido@far.fiocruz.br gen presentation or clonal expansion, and is able to produce a large repertory of Th1-, Th2-, and Th17-associated cytokines [2][3][4][5][6]. These characteristics make γδ T cells a crucial first line of defense during infection, tissue damage, or stress.γδ T cells have been shown to migrate into the airways during allergic inflammation highly controlled by a chemotactic gradient of chemokines produced in tissue [5,[7][8][9][10][11]. We have previously demonstrated that allergen-induced γδ T-cell accumulation is * These authors contributed equally to this work.…”