In addition to cell surface markers by flow cytometry, human multi-lobed neutrophils were readily detected in the chimeric bone marrow spreads by incubating with anti-human PR3 hIgG or anti-human MPO hIgG derived from patients with systemic vasculitis and visualizing the binding with fluorescently conjugated anti-human IgG (Fig. 1G). This evidence concerns the gene MPO and necrotizing vasculitis.