Immunohistochemical detection of GM-CSF in the lungs of patients with iPAP. Lung tissue biopsy specimens from 4 patients with iPAP or 4 healthy controls were assessed for the presence of GM-CSF and SP-A by immunohistochemical staining. (A-D) Sections of normal lung. AM (B, arrowheads) and alveolar epithelial cells (B, arrows) were stained red by anti-GM-CSF antibody (A-B). Alveolar epithelial cells stained by anti-GM-CSF antibodies were stained brown by anti-SP-A antibodies on the serial section (C, arrows). Therefore, they were likely to be alveolar type 2 cells. (E-N) Sections of iPAP lung. Alveolar epithelial cells (F, I, L, N, arrows) stained red. Similar cells were stained brown on the serial section (G, arrows). Original magnifications are indicated above each column.