Inflammatory Cells in Lung Disease Associated with Rheumatoid Arthritis

Objective Rheumatoid arthritis (RA) is associated with numerous pulmonary manifestations. However, the inflammatory mechanism remains undetermined. We studied the features of inflammatory cells in bronchoalveolar lavage (BAL) fluid and biopsy lung tissue from patients with RA-associated lung disease. Methods BAL findings were statistically compared between diseases. We divided RA patients into two groups, airway lesion group (AW) and interstitial lesion group (INT) according to predominant HRCT findings and compared the BAL findings. We immunohistochemically stained lung tissue for CD4, CD8, CD20, and CD163 and counted the immunopositive cells in five different regions. Patients Twenty patients fulfilling the Japanese criteria for RA, 13 patients with systemic sclerosis (SSc), and 21 patients with polymyositis and dermatomyositis (PM-DM) with pulmonary disease detected by high-resolution CT (HRCT) were enrolled in this study. Results As for BAL in RA, we found a lower lymphocyte frequency with higher CD4/8 ratio compared with PM-DM and a higher neutrophil percentage than both PM-DM and SSc. Nine and eleven patients with RA were classified into AW and INT groups, respectively. BAL findings did not differ between the two groups. Immunohistochemically, most CD4+ and CD20+ lymphocytes were accumulated in lymphoid follicles and in the alveolar wall and T-lymphocytes; in particular CD8+ lymphocytes were predominant in lung interstitium. Conclusion These results suggest that 1) neutrophils may play an important role, 2) the inflammatory mechanism may be similar between airway lesion and interstitial pneumonia, and 3) CD8+ lymphocytes may be major inflammatory cells in lung interstitium in RA-associated interstitial lung disease.