Regenerative process of hyaline membrane disease. Electron microscopic, immunohistochemical, and biochemical study.

Regression of hyaline membrane disease was studied with light and electron microscopy, immunohistochemistry using the factor VIII-related antigen, lysozyme, alpha 1-antichymotrypsin and surfactant apoprotein antisera, and biochemical quantitation of surfactant disaturated phosphatidylcholine. The repair of hyaline membrane disease occurred by two processes; expansion of atelectatic alveoli and absorption of the hyaline membrane. Regenerative type II pneumocytes containing numerous organelles and lamellar inclusion bodies could be seen three days following birth. Disaturated phosphatidylcholine content also increased three days after birth. Absorption of the hyaline membrane occurred on part of several types of cells such as intra-alveolar macrophages and spindle-shaped cells appearing below or above the hyaline membrane. Intra-alveolar macrophages showed positive immunoreactivity with lysozyme and alpha 1-antichymotrypsin antisera. The spindle-shaped cells indicated negative immunoreactivity with these antisera, though some of them showed positive immunoreactivity with surfactant apoprotein or factor VIII-related antigen antisera. It thus appears that cells of different origin may possibly participate in the absorption of hyaline membrane.