Diphenylene iodonium is an inhibitor of the respiratory burst-generating NADPH 
oxidase of phagocytes. The effect of this compound on human monocyte-derived 
macrophages and its usefulness in exploring the antimicrobial mechanisms of 
phagocytes was examined. 1 microM diphenylene iodonium inhibited hydrogen 
peroxide production by human macrophages and the activity of these cells against 
Toxoplasma gondii. At this concentration macrophage degranulation was 
unaffected.