Bronchoalveolar lavage in hypersensitivity pneumonitis: a series of 139 patients.

Hypersensitivity pneumonitis (HP) is characterized by a lymphocytic alveolitis, classically delineated by an increase of CD8+ lymphocytes, with an inversion of the CD4+/CD8+ ratio. The aim of this study is both to describe the yield and cell bronchoalveolar lavage (BAL) profile and to revisit the assumption of low BAL CD4/CD8 ratio in the diagnosis of HP. A multicentric study was conducted on 139 patients who fulfilled the standardized diagnostic criteria of HP, mainly affected by farmer's lung.