The measurement of cytochrome b559 in polymorphonuclear leukocytes and macrophages in the presence of hemoglobin or mitochondrial cytochromes.

A cyanide-insensitive b-type cytochrome (cytochrome b559) is involved in the respiratory burst of phagocytes. Spectroscopic measurement of its content in polymorphonuclear leukocytes or macrophages is complicated by signals arising from contaminating Hb or mitochondrial cytochromes upon reduction by dithionite. These interferences can be overcome by reducing the sample with dithionite, aerating it, and reducing it a second time with dithionite, in the presence of 10 microM cyanide. Cyanide suppresses the response of the interfering proteins to the second dithionite reduction. This modified method allows an accurate determination of the content of cytochrome b559 using smaller numbers of cells than previously feasible.