ABSTRACT
BACKGROUND: Cellular analysis of bronchoalveolar lavage fluid (BALF) is a useful diagnostic tool for interstitial lung diseases (ILDs). The lymphocytes in BALF consist of CD3+CD4+ T cells (T4), CD3+CD8+ T cells (T8), and a few B cells. However, sometimes, an increased number of CD3+CD4-CD8- T cells (double-negative T cells, DNTs) are noted in BALF. It is known that DNTs in the blood are associated with immunoregulation and autoimmune diseases. However, there are only few studies on DNTs in BALF. We evaluated the DNTs in BALF in patients with pulmonary diseases. METHODS: Immunophenotyping results of the BALF obtained from 122 pulmonary disease patients over an 8-yr period were reviewed. T-lymphocyte subsets (T4, T8, and DNT) and inflammatory markers were analyzed for each group of clinical diagnosis. T-lymphocyte percentage of more than 15% of the total cells was defined as BALF lymphocytosis, and DNT percentage of more than 5% of T lymphocytes was defined as high DNT. RESULTS: The most frequent diseases found in the patients were pneumonia (31.6%), autoimmune-related ILDs (18.0%), hypersensitivity pneumonitis (10.7%), and organizing pneumonia (10.7%). However, the occurrence of autoimmune-related ILDs was significantly high (40%) in patients with lymphocytosis and high DNT (P=0.002). All lung cancer patients showed lymphocytosis with high DNT. In addition, CD3-signal intensities of DNTs were significantly higher than those of other T-lymphocyte subtypes (P=0.003). CONCLUSION: The number of DNTs in BALF was increased in patients with autoimmune-related ILDs and lung cancer. High DNTs in BALF are useful as supportive diagnostic tools for autoimmune-related ILDs.