The MPO-H2O2-chloride antimicrobial system (taken from Goebel and Dinauer50 ). NADPH indicates reduced nicotinamide adenine dinucleotide phosphate; O2, superoxide anion; and HOCI, hypochlorous acid. Illustration by Kenneth Probst. Adapted with permission from Journal of Leukocyte Biology. Klebanoff SJ. Myeloperoxidase: a friend and foe. J Leukoc Biol. 2005;77:598-625.46