T-LYMPHOCYTE SUBSETS IN BRONCHOALVEOLAR LAVAGE: A FLOW-CYTOMETRIC ANALYSIS AND ITS IMPORTANCE IN THE DIFFERENTIAL DIAGNOSIS OF SARCOIDOSIS

Background - The immunophenotyping of lymphocyte subsets in bronchoalveolar lavage (BAL) is of importance in the differential diagnosis of interstitial lung diseases. The main intent for lymphocyte population subtyping in BAL fluid is finding those diseases with increased lymphocytic cell infiltration in the affected organ such as sarcoidosis and asbestosis. Methods - A dual color flow-cytometric analysis was performed to identify the percentages of total T (CD3+) lymphocytes, T-helper (CD4+) lymphocytes, cytotoxic (CD8+) T-lymphocytes, CD4/CD8 ratio, CD19+ B-lymphocytes, and CD16+56 natural killer cells in the BAL fluid of untreated patients with sarcoidosis, tuberculosis, and other interstitial lung diseases. Lymphocytes were gated on the basis of their expression of CD45 and their side scatter properties. T-lymphocyte subsets were analyzed in 37 patients with sarcoidosis, tuberculosis, nonsarcoidosis, and nontuberculosis. A p value of less than 0.05 was regarded as statistically significant for the results obtained. Results - The results presented here show that a high percentage of CD3+ and CD4+ T- lymphocytes as well as a high CD4/CD8 ratio were observed in the BAL fluid of the patients with sarcoidosis when compared with other interstitial lung diseases. An analysis of CD4/CD8 ratio exhibited that a CD4/CD8 ratio of 4:1 had a positive predictive value of 95% in distinguishing sarcoidosis from other pulmonary diseases. Conclusion - The high specificity of the procedure suggests that it may be used routinely for the analysis of lymphocytes in BAL fluid for the differential diagnosis of sarcoidosis.