Bronchoalveolar lavage is a safe and simple technique to evaluate lung disease related to exposure to mineral dusts. The aim of this study was to characterize the lymphocyte subsets in bronchoalveolar lavage of patients with silicosis. Bronchoalveolar lavage was carried out in 26 workers with different forms of silicosis: simple form (n = 12), complicated (n = 13) and 1 patient with acute form of the disease. As a control group, 7 healthy individuals were included. Compared to the control group, silicotic patients showed intense pleocytosis constituted mainly by alveolar macrophages with slight lymphocytosis. Lymphocyte subsets present in the bronchoalveolar fluid (BAL) of normal individuals were mature lymphocytes with phenotype CD2+TCRab (87.3%) and only 2.9% were CD2+TCRgd. CD4/CD8 ratio was 1.8 with few (16%) immature double negative T cells subsets (CD4-CD8-). In contrast, silicotic patients showed reduction of the more mature lymphocyte subset CD2+CD4+, CD2+CD8+ and a great increase (47%) of immature (CD4-CD8-) T cell subsets. No increase in the NK (CD56+) cell population was observed. Biochemical analysis of protein contents and determination of the Ig/albumin ratio characterized local immunoglobulin production within the pulmonary microenvironment. Furthermore, lack of increase of plasma cells, as well as the maintenance of the percentage of B lymphocyte population (CD19+) in the BAL of silicotic patients, favors the hypothesis that the cells responsible for Ig production are possibly located in the interstitial space. Altogether the results suggest development of lymphopoiesis and tertiary lymphoid tissue within the pulmonary microenvironment during the clinical course of silicosis.

Keywords: bronchoalveolar lavage, lymphocyte subsets, silicosis, immunophenotyping