ULTRASTRUCTURAL-STUDY ON HUMAN LUNG IN ALVEOLITIS VERSUS PULMONARY FIBROSIS

Lung specimens of 21 patients with diffuse interstitial lung disease w ere examined. The present ultrastructural study outlines the topograph y and distribution of inflammatory changes in the interstitium, endoth elium, and in pneumocytes and phagocytes. Alveolitis is characterized by marked regenerative activity of type II pneumocytes (cuboid metapla sia), intraluminal macrophage accumulation, endothelial swelling, mult ilamination of the. endothelial basement membrane, pericapillary edema , and primarily by cellular infiltrates in the interstitial space. The most prominent feature of the interstitium in pulmonary fibrosis is t he lack of immunoinflammatory cells. In some areas there is a marked a bsence of alveolar lumen while only a small number of macrophages are present in the remaining alveolar lumen. Most of the capillaries in th e fibrous septum have been destroyed. Ultrastructural studies of lung biopsies in patients with diffuse interstitial lung disease allow the differentiation between alveolitis and pulmonary fibrosis and thus con tribute to a therapeutic decision.