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Induction of allergic inflammation in the lungs of sensitized sheep after local challenge with house dust mite
Author(s) -
Bischof R. J.,
Snibson K.,
Shaw R.,
Meeusen E. N. T
Publication year - 2003
Publication title -
clinical and experimental allergy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 154
eISSN - 1365-2222
pISSN - 0954-7894
DOI - 10.1046/j.1365-2222.2003.01534.x
Subject(s) - house dust mite , immunology , allergen , eosinophil , immunoglobulin e , medicine , bronchoalveolar lavage , allergic inflammation , allergy , asthma , lung , mite , biology , antibody , botany
Summary Background Previous sheep models of asthma are based on sheep sensitized to nematode (Ascaris) allergens and these have been used to evaluate the physiological and pharmacological effects of potential anti‐asthma agents. The immunological mechanisms associated with the allergic response in sheep lungs has not been examined in detail. Objective To develop an experimental sheep model of allergic lung inflammation based on a relevant major human allergen, house dust mite, and to define the immunological features of the allergic response in this model. Methods Sheep immunized subcutaneously with solubilized house dust mite extract were given a single bronchial challenge with house dust mite. Bronchoalveolar lavage (BAL) and peripheral blood leucocytes were collected before and after challenge for flow cytometry, and tissue samples were taken post‐mortem (48 h post‐challenge) for histology and immunohistochemical analyses. Results Immunizations with 50 μg house dust mite induced an allergen‐specific IgE response in 50 to 60% of sheep (allergic sheep), with higher antigen doses increasing specific IgG 1 but not IgE. Lung challenge of allergic sheep with house dust mite led to the initial recruitment of neutrophils (at 6 h post‐challenge) followed by eosinophils and activated lymphocytes into the lung tissue and BAL, similar to the late‐phase allergic response seen in human asthma. Eosinophil recruitment peaked at 48 h post‐challenge, representing 10 to 33% of BAL leucocytes in allergen‐challenged allergic sheep compared to 0 to 3% in allergen‐challenged control (naïve) sheep. Lymphocytes recovered from the lung after allergen challenge were enriched for CD4 + T cells and were more activated than lymphocytes in blood. There was significant down‐regulation of CD62L (L‐selectin) and CD49d (VLA‐4) expression after allergen challenge on BAL eosinophils and lymphocytes compared to blood. In addition, VCAM‐1 (ligand for VLA‐4) was up‐regulated on blood vessels of allergen‐challenged lungs. Eosinophils, CD4 + T cells and CD45R + B cells were the most prominent leucocytes found in lung tissue 48 h after allergen challenge. Conclusion This study demonstrates, for the first time, the ability of house dust mite to induce allergic responses in sheep lungs. This novel sheep model of allergic lung inflammation using relevant human allergens, exhibits similarities to human asthmatic disease and will be a useful tool for studies of the immunological and physiological mechanisms of allergic asthma.