MPO and Crohn disease: To initially investigate this, we collected samples from patients with UC, Crohn’s disease, and antineutrophil cytoplasmic antibody–associated (ANCA-associated) vasculitis (AAV) positive for myeloperoxidase (AAV-MPO) or proteinase 3 (AAV-PR3) — diseases with well-documented autoimmune and autoinflammatory components.