Oichi Kawanami

Bronchoalveolar lavage is an invaluable means of accurately evaluating the inflammatory and immune processes of the human lung. Although lavage recovers only those cells and proteins present on the epithelial surface of the lower respiratory tract, comparison with open lung biopsies shows that these constituents are representative of the inflammatory and immune systems of the alveolar structures. With the use of these techniques, sufficient materials are obtained from normal individuals to allow characterization of not only the types of cells and proteins present but their functions as well. Such observations have been useful in defining the inflammatory and immune capabilities of the normal lung and provide a basis for the study of lung disease. Lavage methods have been used to characterize inflammatory and immune processes of the lower respiratory tract in destructive, infectious, neoplastic, and interstitial disorders. From the data already acquired, it is apparent that bronchoalveolar lavage will yield major insights into the pathogenesis, staging, and therapy decisions involved in these disorders. (Am J Pathol 97:149--206, 1979).

For a study of the processes and mechanisms of pulmonary structural remodeling in fibrotic lungs and metaplastic squamous epithelial cells in fibrotic alveoli, immunohistochemical, ultrastructural, and light-microscopic morphometric observations were made of the lungs in acute and proliferative stages of diffuse alveolar damage (n = 40) obtained from biopsies and autopsies. Morphometry showed that intraalveolar fibrosis developed in the early proliferative stage and was more prominent than interstitial fibrosis. In the early proliferative stage, activated myofibroblasts migrated into intraalveolar spaces through gaps in the epithelial basement membrane. They then attached to the luminal side of epithelial basement membrane and produced intraalveolar fibrosis and coalescence of alveolar walls. This intraalveolar fibrosis was the essential factor in the remodeled lungs. Albumin, fibrinogen, immunoglobulins, and surfactant apoprotein were present throughout the hyaline membrane. Fibronectin was not found in hyaline membrane of the lesions in early acute stage but was demonstrated in later stages in outer layers of hyaline membranes and in the areas of intraalveolar fibrosis. Fibronectin may be responsible for the migration and proliferation of myofibroblasts in intraalveolar spaces. Metaplastic single-layered and stratified squamous epithelial cells were keratin-positive and surfactant apoprotein-negative. These metaplastic epithelial cells were frequently found in the alveoli with minimal Type II epithelial cell proliferation and in the grossly scarred alveoli.

The topographic distribution, population density, and ultrastructural features of metachromatic cells (mast cells and basophilic leukocytes) were studied in lung biopsies from five control patients and 17 patients with fibrotic lung disorders. The great majority of metachromatic cells were mast cells. The average number of metachromatic cells per square millimeter of tissue section was much larger in patients with fibrotic lung disorders (45.8 +/- 6.5) than in control patients (2.6 +/- 1.6). In control patients, mast cells were most frequently seen in subpleural and perivascular connective tissue. In contrast, the vast majority of mast cells in patients with fibrotic lung disorders was present in thickened, fibrous alveolar septa; mast cells also were found within the alveolar epithelial layer and alveolar lumina. The quantitative distribution of different types of mast cell granules differed in the two groups of patients: granules composed of scrolls were more frequent in control patients, and granules of the combined type (containing mixtures of different components within the same granule) were more frequent in patients with fibrotic lung disorders. Mast cells in the latter patients appeared to migrate through defects in the basement membrane into the epithelial layer and alveolar lumina; mast cells in these areas often showed reduced numbers of granules and disorganized granule content. These changes suggest that pulmonary parenchymal mast cells in fibrotic lung disorders undergo a chronic process of partial degranulation which differs from that found in anaphylaxis; this chronic release of mast cell products may contribute to the continuing alveolar injury and the ventilation-perfusion inequalities observed in the fibrotic lung disorders.

The ABCA3 gene, of the ABCA subclass of ATP-binding cassette (ABC) transporters, is expressed exclusively in lung. We report here the cloning, molecular characterization, and distribution of human ABCA3 in the lung. Immunoblot analysis using the specific antibody reveals a 150-kDa protein in the crude membrane fraction of human lung. Immunohistochemical analyses of alveoli show that ABCA3 is expressed only in the type II cells expressing surfactant protein A. At the ultrastructural level, ABCA3 immunoreactivity was detected mostly at the limiting membrane of the lamellar bodies. Since members of the ABCA transporter family are known to be involved in transmembrane transport of endogenous lipids, our findings suggest that ABCA3 plays an important role in the formation of pulmonary surfactant in type II cells.

Pulmonary granulomata of sarcoidosis are composed primarily of mononuclear phagocytic cells that are probably derived from blood monocytes. To evaluate the concept that recruitment of blood monocytes to the sarcoid lung is mediated by chemoattractants produced by immune effector cells within the lung, we obtained mononuclear cells from lung and blood of six patients with active pulmonary sarcoidosis, six normal subjects, and six patients with active idiopathic pulmonary fibrosis and studied their ability to secrete a chemotactic factor for monocytes. Lung T lymphocytes from all sarcoidosis patients, but not from normal subjects or patients with idiopathic pulmonary fibrosis, spontaneously secreted such a mediator. Lung T lymphocytes from patients with sarcoidosis secreted more monocyte chemotactic factor than did blood T lymphocytes from the same patients. The accumulation of monocytes in the lung in patients with pulmonary sarcoidosis may be mediated by local production of monocyte chemotactic factor by lung T lymphocytes.