XDH and Sepsis: As for the systems that generate ROS in sepsis, these are complex, including NADPH oxidase (NOX) and dual oxidase enzymes (DuOX); mitochondrial respiration and dysfunction; the activities of cyclooxygenases and lipoxygenases; xanthine oxidoreductases (XOR); the effects of ischaemia reperfusion injury; NO production by NOS enzymes; and loss of homeostatic control for iron recycling, allowing for production of directly damaging ROS.