Conclusion
Although pathophysiological mechanisms of MPO-AAV involved innate immunity (e.g., role of PAD4, effect of NETs, activation of cAP, and etc.) and adaptive immunity (e.g., generation of MPO-ANCA) and the complex relationships between them, our research result showed that PAD4 as well as MPO-ANCA was independent factor affecting the clinical damage of MPO-AAV. Since PAD4 inhibitor could decrease NETs and MPO-ANCA generation in animal model of MPO-AAV[37], It is tempting to imagine that PAD4 might be a potential new therapeutic target for MPO-AAV.