Integrin alpha E beta 7 expression on BAL CD4+, CD8+, and gamma delta T-cells in bleomycin-induced lung fibrosis in mouse

CD4, CD8, and gamma delta T-cells located in the epithelium express the integrin alpha E beta 7 that binds to E-cadherin on the epithelium. gamma delta T-cells mediate specific cellular immune functions and can recognize damaged cells directly. It was, therefore, of interest to analyse the presence of gamma delta T-cells and the expression of alpha E beta 7 on gamma delta T-cells in the bleomycin (BLM) model of pulmonary fibrosis. Lung fibrosis was induced by a single intratracheal instillation of BLM (0.125 U . mouse(-1)), and bronchoalveolar lavage (BAL) T-cell subpopulations were examined at various time-points for the expression of the integrin alpha E beta 7 by flow cytometry. CD4+ T-cells accounted for about 40% of the lymphocytes, compared to about 10% of CD8+ T-cells and 10-14% gamma delta T-cells. Within the CD4+ T-cell population the proportion of alpha E beta 7+ cells decreased between Days 2 and 22 from 36 to 11%. The percentage of alpha E beta 7+ CD8+ T-cells increased at the same time from 4 to 68%. However, more than 80% of the gamma delta T-cells in BAL fluid expressed alpha E beta 7 at all time-points. The surface-expression of this integrin on gamma delta T-cells was 2-3 times higher than on CD4+ or CD8+ T-cells. This predominant expression of alpha E beta 7 on gamma delta T-cells suggests a role for these cells in the pathogenesis of bleomycin-induced lung fibrosis.