T lymphocytes expressing the alpha E beta 7 integrin are localized and selectively retained in mucosal tissues. To investigate a potential relationship between alpha E beta 7 expression and pulmonary inflammation, the distribution of alpha E beta 7-bearing CD4+ and CD8+ T cells in peripheral blood and bronchoalveolar lavage (BAL) fluids obtained from patients with allergic asthma, sarcoidosis, hypersensitivity pneumonitis, and idiopathic pulmonary fibrosis (IPF) was determined. In contrast to the distribution in peripheral blood, BAL fluid from these patients contained high number of cells expressing alpha E beta 7 with markedly different expression patterns on CD4 or CD8 cells as well as among the various diseases. Despite similar numbers of activated CD4 cells, alpha E beta 7+CD4+ T cells ranged from 15% in asthmatics to 70% in IPF. In contrast, even in normal individuals, 60% to 90% of BAL fluid CD8+ T cells express alpha E beta 7, suggesting differential induction mechanisms on CD4 and CD8 cells. In vitro experiments revealed that a substantial proportion of peripheral blood CD+ T cells express alpha E beta 7 after stimulation with anti-CD3 antibodies, and up to 80% positive cells were found after the addition of TGF-beta. In contrast, less than 10% of CD4 cells express this particular integrin after in vitro stimulation, and the presence of TGF-beta only increased the number to 30%. Supernatants from in vitro-activated BAL cells as well as concentrated BAL fluid from patients with high alpha E beta 7 expression had no further enhancing effect. However, crosslinking of alpha 4 beta 1-, but not beta 2-integrins, significantly increased the number of alpha E beta 7 expressing CD4+ and CD8+ T cells, even in the absence of TGF-beta. These data indicate that in addition to TGF-beta, the interaction of particular T-cell subsets with specific endothelial cell and extracellular matrix proteins may upregulate alpha E beta 7 integrin expression and thereby contribute to the selective accumulation of these cells in inflammatory lung diseases.

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