Confocal microscopic images of immunohistochemical double staining for the autoantibodies against GM-CSF. (A-H) Lung tissue from a patient with iPAP. (I-L) Histologically normal lung tissue from a patient with lung cancer. These tissues were stained with hematoxylin-eosin (A, E, I), FITC-conjugated antihuman IgG (green; B, J), FITC-conjugated antimurine IgG (green; F), PE-conjugated GM-CSF (red; C, K), and PE-conjugated G-CSF (red; G). A combination of both channels (B-C, F-G, J-K) clearly demonstrates the occurrence of the autoantibodies in the alveolar filling materials of the iPAP lung (D) but not in normal lung (L).