CD4 and pulmonary fibrosis: In the bleomycin (BLM) model of lung fibrosis induced by a single intratracheal instillation of BLM, >80% of the γδ T cells in bronchoalveolar lavage (BAL) fluid expressed the E-cadherin binding αEβ7 integrin, at levels that were 2–3 times higher than on CD4+ or CD8+ T cells, suggesting a critical role for γδ T cells in the pathogenesis of BLM-induced lung fibrosis.23 After exposure to BLM, but not to Schistosoma mansoni eggs, the interleukin (IL)-17A that was produced by CD4+ and γδ T cells induced significant neutrophilia and pulmonary fibrosis.