This strain is an Mpo gene knockout (KO) mouse model, constructed by knocking out all protein-coding sequences of the Mpo gene (the homologous gene of human MPO) in mice using gene editing technology. Studies have shown that Mpo KO mice exhibit almost no physiological abnormalities under normal conditions and are only more susceptible to certain pathogen infections. In ANCA-associated vasculitis (AAV) studies, Mpo KO mice are widely used to prepare mouse auto-MPO antibodies. The specific method involves immunizing Mpo KO mice with recombinant mouse MPO antigen as donors to produce anti-mouse MPO auto-antibodies, and then injecting the antibodies into normal mice (or target humanized mice) to induce ANCA-associated vasculitis and use them for targeted drug testing. This method is the most commonly used approach in ANCA research. It has been applied to the preclinical efficacy testing of avacopan, a C5aR antagonist approved by the FDA for the treatment of ANCA.