Objective: Patients with mixed connective tissue disease (MCTD) exhibit clinical features of systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and polymyositis and dermatomyositis (PM-DM). The objective of this study was to clarify differences in BAL findings and immunophenotypes of BAL fluid (BALF) cells of patients with interstitial lung disease associated with these diseases.
Methodology: We were unable to recruit a sufficient number of SLE patients with lung disease. We compared immunophenotypes of lymphocytes and alveolar macrophages (AM) in BALF of 20 MCTD patients with those of 21 SSc and 27 PM-DM patients and tested the relationships between immunophenotypes and pulmonary function in MCTD.
Results: MCTD patients had a significantly higher CD4/CD8 ratio with more CD4 positive lymphocytes than PM-DM patients (P = 0.025). In AM phenotypes, MCTD patients had a significantly lower percentage of CD71 positive AM compared with SSc patients (P = 0.023). DLCO was negatively related to absolute numbers of CD8 positive lymphocytes (R = -0.517, P= 0.033).
Conclusions: CD4 positive lymphocytes in BALF were increased in MCTD compared to PM-DM patients, while CD71 positive AM were decreased in MCTD compared to SSc patients. CD8 positive lymphocytes correlated negatively with DLCO measurements in MCTD patients.