Expression of mucosa-related integrin αEβ7 on alveolar T cells in interstitial lung diseases

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The expression of αEβ7 integrin has been related to the selective retention of lymphocytes in mucosal tissues of gut, urogenital tract and lung. To identify potential disease-associated αEβ7 expression patterns on cells accounting for lymphocytic alveolitis in interstitial lung disease (ILD), αE expression on CD4+ and CD8+ T cell subsets was evaluated by dual-colour flow cytometry in peripheral blood and bronchoalveolar lavage fluid (BALF) of patients with idiopathic pulmonary fibrosis (IPF; n = 18), hypersensitivity pneumonitis (HP; n = 20) and sarcoidosis (n = 44) in comparison with healthy controls (n = 15). In both healthy individuals and all patient groups the proportion of αE-bearing T cells in peripheral blood was <2%, whereas the vast majority of alveolar CD8+ T cells consistently co-expressed αE. Absolute alveolar CD8+αE+ cell numbers/ml were up to 30-fold increased in HP patients. Proportions of αE-bearing CD4+ cells in BALF were significantly elevated in IPF (74·0 ± 2·7%) and HP (70·0 ± 2·4%) compared with normals (30·0 ± 1·8%) (mean ± s.e.m.; P < 0·01). In sarcoidosis, the αE expression on BALF CD4+ cells displayed subgroup dependency: proportions significantly lower than normal were noted in chest radiographic stage I (14·3 ± 1·5%), but increased proportions in stages II (50·0 ± 3·8%) and III (64·0 ± 4.8%). Correlations between common markers of T cell activation or BALF transforming growth factor-beta (TGF-β) bioactivity and αE expression were not noted. We conclude that the vast majority of alveolar CD8+ T cells consistently express αEβ7 and that distinct patterns of αEβ7 expression on alveolar CD4+ lymphocytes in sarcoidosis are related to the diverse manifestations of the sarcoid inflammatory process in the lung.

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