Lymphocyte subsets in lung tissues of interstitial pneumonia associated with untreated polymyositis/dermatomyositis

This study was designed to evaluate the distribution of lymphocyte subsets in lung specimens obtained by surgical lung biopsy from 12 patients with interstitial pneumonia associated with untreated polymyositis/dermatomyositis (PM/DM). Differences of histological findings and distributions of lymphocyte subsets between PM and DM were also evaluated. Distributions of B lymphocytes, CD4-positive T lymphocytes, and CD8-positive T lymphocytes were evaluated immunohistochemically. Interstitial pneumonia was pathologically classified as basically nonspecific interstitial pneumonia (NSIP) in all patients. Immunohistochemically, the distribution of B lymphocytes was mostly restricted to inside and/or around lymphoid follicles. The CD4-positive T lymphocytes were distributed diffusely in fibrotic areas and unrelated to lymphoid follicles. Most CD8-positive T lymphocytes were diffusely distributed, especially in relatively normal alveoli. There were no significant differences in the distribution of lymphocyte subsets between PM and DM. Although the distribution of B lymphocytes and CD4- and CD8-positive T lymphocytes in the lung were different, there were no significant differences in distributions of lymphocyte subsets between PM and DM.