Localization of organ-specific antigens in mouse lung by light and electron microscopy

Rabbit antisera were raised against whole homogenate and a saline soluble fraction of C57BL mouse lung. After absorption with other mouse organs, both antisera gave specific staining of bronchiolar epithelial and single alveolar cells, using the indirect immunofluorescence and indirect immunoperoxidase techniques on both acetic-alcohol-fixed paraffin-embedded and unfixed frozen 5 micrometer sections. Improved resolution by light microscopy was achieved with 1 micrometer sections of formaldehyde-fixed Araldite-embedded material stained by an indirect immunoperoxidase method after the Araldite had been treated with saturated alcoholic NaOH for 5 min. Clara cells and type II pneumocytes were identifiable as sites of the lung-specific immune reaction. At the electron microscopic level the reaction was localized over the granules of bronchiolar Clara cells. The lamellar bodies of type II pneumocytes were extracted in the ultrathin sections and no immune reaction was observed.