Lymphocyte subsets in lung tissues of non-specific interstitial pneumonia and pulmonary fibrosis associated with collagen vascular disorders: Correlation with CD4/CD8 ratio in bronchoalveolar lavage

This study was designed to evaluate the distribution of lymphocyte subsets in lung specimens that were obtained by open-lung biopsy from 8 patients with idiopathic nonspecific interstitial pneumonia/fibrosis (NSIP) and 10 patients with pulmonary fibrosis associated with collagen vascular disorders (PF-CVD). Distributions of B lymphocytes, CD4-positive T lymphocytes, and CD8-positive T lymphocytes were evaluated immunohistochemically and compared with the cell composition in BALF. Correlation between CD4/CD8 ratios in bronchoalveolar lavage fluids (BALF) and CD4/CD8 ratios in lung tissues was also examined. B lymphocytes were mostly restricted in lymphoid follicles. CD4-positive T lymphocytes were observed inside and around lymphoid follicles and in the thick fibrotic wall of reconstructed alveoli with fibrosis. In contrast, CD8-positive T lymphocytes were diffusely distributed, especially in relatively thin alveoli. Correlation was weak between CD4/CD8 ratios in lung tissue and CD4/CD8 ratios in:BALF. However, even in patients with very low CD4/CD8 ratios in BALF, many CD4 lymphocytes were observed in lung tissues, suggesting that CD8-positive lymphocytes diffusely distributed in thin alveolar architecture were more easily recovered in BALF than CD4-positive lymphocytes. Therefore, a low CD4/CD8 ratio in BALF may indicate that the alveolar structure was not severely reconstructed by fibrosis, This is the first report that compared lymphocyte subsets in lung tissues and in BALF.