Background : This study was purposed to find out the differences in the lymphocyte subsets and differential cell counts of the bronchoalveolar lavage (BAL) fluid in patients with interstitial lung disease (ILD) and to analyze the differences according to their ages, gender and smoking habits.
Methods : BAL fluid samples of 141 ILD patients were examined for lymphocyte subsets and differential cell counts, and the differences among the patients were analyzed according to their diseases. Then, within the three most common disease groups, the differences were further analyzed by the age, gender and smoking habit of the patients.
Results : There were no statistically significant differences in total cell counts (per millimeters of BAL fluid) among the patient groups with each ILD. However, significant differences were observed in the percentages of neutrophils, lymphocytes, eosinophils, and macrophages of BAL fluid. Also, in lymphocyte subset analyses, the percentages of total T cells, B cells, CD4+ T cells, CD8+ T cells, CD4/CD8 T cell ratios, and NK cells were significantly different among the patients with each ILD. However, within the same disease group, there were no differences in differential cell counts and lymphocyte subset analyses according to the age, smoking habit, and gender of the patients.
Conclusions : Although the age, smoking habit and gender did not have an effect on the BAL fluid analyses among the patients with the same ILD, there were significant differences among the patients with each ILD; therefore, the differential cell counts and lymphocyte subset analyses of BAL fluid can be useful in differential diagnosis for determining the types of ILD.

Keywords: Bronchoalveolar lavage, Differential cell count, Lymphocyte subset