However, neutrophil infiltration followed by generation of apoptotic cells or necrotic debris and microabscesses precedes MGC lining sites of inflammation.14 Unlike, MPO-ANCA-associated MPA, in which rodent models have been very successfully developed,15–18 rodent models of PR3-ANCA disease, and specifically the granulomatous manifestations, have universally failed to replicate human disease.19 20 This is thought to be in part due to differences between human and rodent PR3 biology.21 Here, MPO is linked to microscopic polyangiitis.