Expression of Ia-like (DR) antigen on human alveolar macrophages isolated by bronchoalveolar lavage.

Alveolar macrophages isolated by bronchoalveolar lavage from nonsmoking patients with sarcoidosis, interstitial pulmonary fibrosis (DIF), and normal volunteers were examined for surface expression of Ia-like (DR) antigen using a monoclonal antibody technique. We found increased percentages of alveolar macrophages expressing DR antigen in the 8 patients with sarcoidosis (77 +/- 3%) and the 7 patients with DIF (78 +/- 3%) over that in the 9 healthy, nonsmoking volunteers (21 +/- 5%, p less than 0.05). Four patients, 2 with DIF and 2 with sarcoidosis, were studied before and 3 months after initiation of therapy. A decrease in DR antigen expression was found to be associated with clinical improvement. Alveolar macrophages from 3 patients were studied serially in culture, with a steady decrease in DR antigen expression with time. We conclude (1) that alveolar macrophages from patients with sarcoidosis and DIF are in a state of heightened activity, and (2) that DR antigen expression may be an indicator of disease activity.