Chronic granulomatous disease (CGD) is characterized by an absent or reduced function of the respiratory burst, which is the intracellular process in neutrophils that is dependent upon the enzyme NADPH oxidase, which produces oxygen free radicals used to kill phagocytized organisms. Flow cytometry can be employed to measure this respiratory burst. In the panel below at the left, unstained granulocytes display minimal measurable autoflourescence. When the laser-sensitive dye dihydrorhodamine123 is added, there is an increase in fluorescence from oxidation of the dye, as shown in the right panel:

When phorbol myristate acetate (PMA) is added, normal granulocytes undergo an oxidative burst, oxidizing the dye and increasing the fluorescence, as seen in the left panel below. However, granulocytes from a patient with CGD do not display this burst, as shown in the right panel: