Analysis of lymphocyte subsets in bronchoalveolar lavage fluid of patients with dermatomyositis/polymyositis-associated interstitial lung disease

Objective To explore the cell counts and distribution features of lymphocytes in bronchoalveolar lavage (BAL) fluid of the patients with dermatomyositis/polymyositis-associated interstitial lung disease (DM/PM-ILD). Methods Total 16 patients with DM/PM-ILD underwent BAL and got BAL fluid. The cells in BAL fluid were counted in all and in differentiation. The lymphocyte subsets in BAL fluid and peripheral blood were detected by flow cytometry. The lymphocyte subsets included CD3⁺ total T cells, CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, CD3^-CD16⁺CD56⁺ NK cells, and CD3^-CD19⁺ B cells. The counts of total cells and the percentages of lymphocyte subsets in BAL fluid were compared between DM/PM-ILD group and normal control. The percentages of lymphocyte subsets were compared between BAL fluid and peripheral blood in DM/PM-ILD patients. Results The percentages of different lymphocyte subsets in peripheral blood were normal except lowered percentages of CD4⁺ T cell, NK cell, and B cell in one patient. There were more cells in BAL fluid of DM/PM-ILD group than in normal control. Moreover, lymphocytes significantly predominated (by 15%). The percentages of CD3⁺ total T cell and CD8⁺ T cell in BALF of DM/PM-ILD patients were more than those in normal control, and more than those in peripheral blood of patients significantly; the percentage of NK cell was less than in normal control; and the difference of B cell percentages was not significant between DM/PM-ILD group and normal control. The percentages of NK cell and B cell in BALF were all less than those in peripheral blood in DM/PM-ILD patients. Conclusion There are significantly elevated lymphocytes and the imbalance of lymphocyte subsets in BAL fluid of DM/PM-ILD patients, especially for CD8⁺ T lymphocytes, which may play an important role in the development of ILD in DM/PM.