Cytochemistry of type II pneumocytes in Chediak-Higashi syndrome of mice

Abstract

The type II pneumocytes of beige mice with the Chediak-Higashi syndrome (CHS) have been compared ultrastructurally and histochemically with those of normal black mice in both newborn and adult animals. In normal black mice the inner face of the limiting membrane of lamellar bodies near the cell surface revealed continuous dialyzed iron (DI) staining as did the luminal surface of the cell. The periodate-thiocarbohydrazide-silver proteinate (PA-TCH-SP) method stained selectively the luminal surface of the granular pneumocyte together with multivesicular bodies and the inner face of the limiting membrane of lamellar bodies, in normal black mice thus supporting the role of multivesicular bodies as precursors of lamellar bodies. The beige mice lacked the layer of continuous DI staining lining the superficial lamellar bodies. Moreover, the PA-TCH-SP staining was negligible on the limiting membrane of large lamellar bodies in beige mice. Immunostaining for lysozyme appeared weaker in the large lamellar bodies of type II pneumocytes of the beige mice. Peroxisomes were normal in size but somewhat increased in number in type II pneumocytes of beige mice. The multivesicular bodies as well as the lamellar bodies increased in size and decreased in number in the beige mice and, in some cell profiles, multivesicular bodies or lamellar bodies appeared to be fusing. Since the multivesicular bodies are thought to be precursors of lamellar bodies, these findings indicate that atypical fusion of the lysosomes in type II pneumocytes occurs at early to late stages of maturation. Newborn beige mice disclosed a greater and more consistent increase in size of the lamellar bodies than did adult beige mice. Compared with newborn black mice the newborn beige mice revealed fewer secreted lamellar bodies in the alveolar space. The cytochemical and morphological changes in lamellar bodies and their precusor multivesicular bodies in type II pneumocytes of beige mice are interpreted as resulting from increased fusion of the precursor bodies and lamellar bodies with one another. Impaired secretion of lamellar bodies possibly also contributes to increased size of lamellar bodies and content of lamellar body material in granular pneumocytes of beige mice.