Fig. 5.

ANCA-stimulated necroptosis in circulating BM-derived cells induces NCGN. (A–F) NCGN was induced in MPO-deficient mice immunized with murine MPO that were subsequently irradiated and transplanted with either WT or RIPK3-deficient (Ripk3^−/−) BM. (A–F) RIPK3 deficiency significantly reduced urine pathology (A) and resulted in strong protection from crescent and necrosis induction (B). Depicted are typical renal sections with (C) low and (E) high magnifications from WT mice, whereas D shows low and F shows high magnifications from RIPK3-deficient mice. (G–K) Exemplary micrograph from a biopsy with active anti-MPO-ANCA–associated NCGN shows fibrinoid necrosis and a cellular crescent; the Insets (G) shows the extent of the crescent in blue, necrosis in red, and tuft in green color. No resident mesangial cells, endothelial cells, podocytes, or intracapillary or infiltrating leukocytes are positive (brown) for p-MLKL. (H) Some of the few tubular segments with epithelial positivity for p-MLKL. (I) Biopsy with active anti-MPO-ANCA–associated NCGN and cytoplasmic positivity for p-MLKL in two neutrophils, recognizable by their typical segmented nuclei (short arrows). The colors in the Left Inset are as above. The neutrophil in the Top Right Inset (arrow) is adjacent to a fibrinoid necrosis area (arrowhead) (I and J). The neutrophil in the Bottom Right Inset is adjacent to a fresh, cellular crescent (long arrows). Both neutrophils in the Right Insets are magnified in the corresponding two frames (J and K) to better appreciate nuclear morphology. Error bars indicate means ± SEM. Comparisons were made using t test or ANOVA; *P < 0.05, **P < 0.01.