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

ABSTRACT: 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.

SUBMITTER: Ghosh S

PROVIDER: S-EPMC4654288 | biostudies-other | 2015 Mar

REPOSITORIES: biostudies-other

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Project description:Allergic asthma is characterized by airway eosinophilia, increased mucin production and allergen-specific IgE. Fc gamma receptor IIb (FcgammaRIIb), an inhibitory IgG receptor, has recently emerged as a negative regulator of allergic diseases like anaphylaxis and allergic rhinitis. However, no studies to date have evaluated its role in allergic asthma. Our main objective was to study the role of FcgammaRIIb in allergic lung inflammation. We used a murine model of allergic airway inflammation. Inflammation was quantified by BAL inflammatory cells and airway mucin production. FcgammaRIIb expression was measured by qPCR and flow cytometry and the cytokines were quantified by ELISA. Compared to wild type animals, FcgammaRIIb deficient mice mount a vigorous allergic lung inflammation characterized by increased bronchoalveolar lavage fluid cellularity, eosinophilia and mucin content upon ragweed extract (RWE) challenge. RWE challenge in sensitized mice upregulated FcgammaRIIb in the lungs. Disruption of IFN-gamma gene abrogated this upregulation. Treatment of naïve mice with the Th1-inducing agent CpG DNA increased FcgammaRIIb expression in the lungs. Furthermore, treatment of sensitized mice with CpG DNA prior to RWE challenge induced greater upregulation of FcgammaRIIb than RWE challenge alone. These observations indicated that RWE challenge upregulated FcgammaRIIb in the lungs by IFN-gamma- and Th1-dependent mechanisms. RWE challenge upregulated FcgammaRIIb on pulmonary CD14+/MHC II+ mononuclear cells and CD11c+ cells. FcgammaRIIb deficient mice also exhibited an exaggerated RWE-specific IgE response upon sensitization when compared to wild type mice. We propose that FcgammaRIIb physiologically regulates allergic airway inflammation by two mechanisms: 1) allergen challenge mediates upregulation of FcgammaRIIb on pulmonary CD14+/MHC II+ mononuclear cells and CD11c+ cells by an IFN-gamma dependent mechanism; and 2) by attenuating the allergen specific IgE response during sensitization. Thus, stimulating FcgammaRIIb may be a therapeutic strategy in allergic airway disorders.

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

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