Figure 1.

Segmental fibrinoid necrosis and crescent formation are the histopathologic features of murine MPO-ANCA GN and are prevented by a B1R antagonist. On the left, from a mouse pretreated with B1R antagonist before receiving anti-MPO, is a representative histologically normal glomerulus 6 days after intravenous injection with 50 µg/g body wt anti-MPO IgG. For comparison, on the right from a mouse pretreated with B1R antagonist vehicle alone before receiving anti-MPO, is a representative glomerulus with segmental fibrinoid necrosis (long arrow) and a cellular crescent (short arrow) 6 days after intravenous injection with 50 µg/g body wt anti-MPO IgG. These anti-MPO–induced crescentic and necrotizing lesions are quantified under different experimental conditions in Figures 2, 3, and 5. Original magnification ×400, hematoxylin and eosin stain.