Discriminative immunophenotype of bronchoalveolar lavage CD4 lymphocytes in sarcoidosis

The diagnosis of pulmonary sarcoidosis relies in part on the observation of alveolar CD4+ lymphocytosis. However, this criterion is not fully discriminative because this anomaly is also found in other types of lung diseases. Among other possible distinctive criteria, we investigated the expression of lymphocyte-addressing molecules, which could differ according to the pathophysiology of lung diseases. We investigated CD103 (alpha(E)beta7 integrin, CD103-beta7), reported to be both expressed on intra-epithelial lymphocytes in mucosal areas, including bronchi, and possibly involved in the recruitment of alveolar lymphocytes. The expression of CD103 was examined on bronchoalveolar lavage lymphocytes from 93 consecutive patients, including 34 patients with CD4+ lymphocytosis. For all patients, the expression of CD19, CD3, CD4, CD8, CD57, LFA1, DR, and CD103 was assessed by flow cytometry. Sarcoidosis seemed remarkably characterized by the lack of CD103 expression on the predominant CD4+ subset. Statistically significant differences were found between patients with sarcoidosis, with other types of CD4+ lymphocytosis, and with other lung disorders in the CD103+ cell levels and in the CD103/CD4 ratio. Combined use of the CD4/CD8 ratio (> 2.5) and the CD103/CD4 ratio (< 0.31) to assess bronchoalveolar lavage lymphocytes is a promising new tool for the diagnosis of sarcoidosis.