Chemiluminescence response of human leukocytes: influence of medium components on light production

Light-producing reactions have been reported to occur after phagocytosis of opsonized particles by human polymorphonuclear neutrophils, eosinophils, and monocytes. Such chemiluminescence appears to be related to the generation of singlet oxygen, superoxide, and hydroxyl radicals, which have also been implicated as microbicidal agents. In examining the influences of various medium components on leukocyte chemiluminescence, we have observed that the amount of light measured is increased by addition of soluble protein, the amino acids tyrosine and tryptophane, or excess zymosan to the reaction medium. These agents appear to produce their effect not by increasing the rate of phagocytosis, but by providing substrate for secondary light-producing reactions. Polystyrene particles do not provide a suitable substrate for such secondary light-producing reactions. This is evidenced by the failure of ingested latex to stimulate high levels of chemiluminescence in the cellular system and their failure to augment light production in two noncellular chemiluminescent reactions. Some of the light generated in the cellular chemiluminescence response may derive from secondary reactions, which occur outside of the phagocyte. Support for this phenomenon is provided by two experiments. In one, addition of supplementary, nonopsonized zymosan to the reaction, after phagocytosis of opsonized zymosan is complete, resulted in an increased level of chemiluminescence. In another, addition of nonopsonized zymosan, together with latex particles, resulted in a significant increase in chemiluminescence. The results of the latter experiment also support our hypothesis that latex does not provide an appropriate substrate for secondary light-producing reactions. These observations suggest that leukocytes activated by phagocytosis generate electronically activated radicals which act intra- and extracellularly and that the amino acids tyrosine and trytophane may provide one substrate through which these agents act.