Cytokine-mediated priming of neutrophil NADPH oxidase activity in patients with acute arthritis (A and B) and iron-deficiency anemia (C and D). Treatment with cytokines and measurement of neutrophil H₂O₂ production were as described in the legend to Fig 2. Data shown are the mean ± 1 SE of six experiments with each patient category. (▧) Patient + PBS; (▨), control + PBS; (▪), patient + FMLP; (□), control + FMLP.