Answer, Image 21: IMMUNOLOGIC
The Masson trichrome stain shows destruction of portions of the capillary loops present in each of the two glomeruli represented. Since only a portion of each glomerulus is affected, the process is classified as segmental. This process is therefore classified as segmental, necrotizing glomerulonephritis. The immunofluorescence stain for IgG shows linear staining of capillary loop basement membranes, indicative of the presence of bound autoantibodies against an intrisic component of the basement membrane. Though the immunofluorescence picture is striking, the anti-basement membrane antibodies are undetectable in the accompanying electron micrograph. (Compare with examples of immune complex glomerulonephritis, in which the complexes are visible in electron micrographs as granular, electron-dense material.) The final image is an immunofluorescence stain for IgG performed on a lung biopsy from a second patient with the same disorder (green indicate positive immunoreactivity, x200). Linear staining of alveolar basement membranes is present.
Diagnosis: Goodpasture's syndrome