ANCHORING FIBRILS - NEW CONNECTIVE-TISSUE STRUCTURE IN FIBROTIC LUNG-DISEASE

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  • 1 January 1978
    • journal article
    • research article
    • Vol. 92  (2) , 389-410
Abstract
EM studies of lung were made and compared in 17 patients with fibrotic lung disease (10 with idiopathic pulmonary fibrosis, 3 with collagen-vascular diseases, 3 with sarcoidosis, and 1 with chronic eosinophilic pneumonia) and in 5 control patients. In control patients, the alveolar epithelial cells were normal, and no hemidesmosomes were present between the plasma membranes and the basal laminae. In comparison, cuboidal alveolar epithelial cells were present in 15 of the patients with fibrotic lung disease. In 9 of these the alveolar epithelial cells were multilayered. In 7 of the latter 9 patients (5 with idiopathic pulmonary fibrosis and 2 with collagen-vascular diseases), the basal laminae of the alveolar epithelial cells were attached to the plasma membranes by hemidesmosomes and to the underlying interstitial connective tissue by anchoring fibrils. These fibrils measured from 4000-6000 .ANG. in lenght and from 200-600 .ANG. in width. One or both ends of the anchoring fibrils inserted into the basal lamina, often forming arcs through which collagen fibrils and connective tissue microfibrils penetrated. Anchoring fibrils showed a complex pattern of transverse banding, which differed from that of collagen and appeared to be symmetric about the center of the fibril. These anchoring fibrils, which resemble those in normal skin and other tissues, were not found in lungs of control patients. In addition, there was a significant correlation between the severity of the pulmonary fibrosis and the presence of anchoring fibrils. In severe fibrotic lung disease, anchoring fibrils may reinforce the attachment of the basal lamina of multilayered alveolar epithelial cells to interstital connective tissue.