MPO-positive macrophages in vitro produce HOCl in response to atherogenic stimuli. Bar graph indicates HOCl production from GM-CSF (100 U/ml)-treated macrophages on day 7 measured by taurine chloramine generation. PMA (300 nmol/L), opsonized zymosan (OZ) (0.2 mg/ml), lysoPC (15 μmol/L), CD40L (5 μg/ml), or cholesterol crystals (1 mg/ml) induced HOCl production in macrophages, but A23187 (1 μmol/L), norepinephrine (10 μmol/L), IL-1β (10 ng/ml), tumor necrosis factor-α (50 ng/ml), and interferon-γ (1,000 U/ml) had no effect (*, P < 0.01 versus vehicle, n = 3).