IMMUNOHISTOCHEMISTRY OF A HUMAN TYPE-1 PNEUMOCYTE-ASSOCIATED PROTEIN IN LUNG

A mouse monoclonal antibody to a human lung lavage protein was raised using proteins, with the potential ability to bind surfactant, as the immunogen. The proteins were isolated from cadaver lung lavage. The an tibody was tested for its reactivity with lung and other organs. It re acted with type I pneumocytes and some of the nonciliated cells in the surface epithelium of distal bronchioles. Staining was also seen in t he cells surrounding the glandular structures, superficial keratinocyt es of the skin, endothelium, and nerve sheath cells. With the exceptio n of bronchiolar cells, the stained cells have a squamous morphology, and this protein may serve as a marker or determinant of this characte ristic of cells. In pathologic lungs some of the cells in air spaces w ith ''bronchiolarization'' of the epithelium exhibited staining for th e protein. It could not be ascertained whether the stained cuboidal ce lls were reactive type II pneumocytes or distal bronchiolar cells. The intraalveolar material in pulmonary alveolar proteinosis did not show remarkable staining for the protein. Even though the protein is not u nique to type I pneumocytes, it may serve as a marker for these cells in the study of their development and biology.