Chemiluminescence of human bloodstream monocytes and neutrophils: an unusual oxidant(s) generated by monocytes during the respiratory burst.

Maximal rates of O2- and H2O2 production by human bloodstream monocytes activated during the respiratory burst by phorbol ester were only about 10% of those of neutrophils. Furthermore, monocytes possess only about 5% of the myeloperoxidase activity of neutrophils and so can only produce low levels of HOCl and related compounds. These combined reductions in O2- generating ability and lower myeloperoxidase levels result in low levels of luminol chemiluminescence stimulated during the respiratory burst of monocytes. However, although monocytes generate much lower levels of O2- and H2O2 than neutrophils, these cells produce comparable rates of PMA-stimulated lucigenin chemiluminescence. Hence, this assay does not accurately reflect the production of either of these two oxidants by activated phagocytes, and further lucigenin must react with some other oxidant(s) via a process which leads to photon emission. This oxidant(s) is not O2-, H2O2, .OH, 1O2 or NO, but is derived from O2- generated during the respiratory burst and is generated in greater quantities by activated monocytes compared with neutrophils. Thus, lucigenin chemiluminescence is an indirect measure of superoxide release.