Effect of Chemoattractants on Chemiluminescence

Abstract

Upon ingestion of particulate matter, polymorphonuclear leukocytes produce a chemiluminescence that can be measured in a liquid scintillation counter. In the experiments reported here, the influence of three chemoattractants and three chemotactic modulators upon the chemiluminescence induced by opsonized zymosan was studied. The chemoattractants investigated (including bacterial factor derived from Escherichia coli , the simple peptide formylmethionylalanine, and activated human complement), which initiate directed movement when presented to cells in a concentration gradient, significantly enhanced zymosan-induced chemiluminescence. In the absence of opsonized zymosan, however, they had no effect on the chemiluminescence response. In contrast, the chemotactic modulators studied (including carbamylcholine, phenylephrine, and cyclic guanosine 5′-monophosphate, which are not chemotactic by themselves but can enhance or depress the movement of polymorphonuclear leukocytes initiated by chemoattractants) produced no enhancement of chemiluminescence. Other experiments were carried out in which neutrophils were pretreated with cytochalasin D, a compound that inhibits phagocytosis by interacting with microfilaments. Under these conditions, the chemiluminescence induced by opsonized zymosan was markedly reduced, but the response resulting from the addition of a chemoattractant to the leukocyte/zymosan mixture was not. This indicates that the chemiluminescence in response to chemoattractants is not dependent on phagocytosis per se. Neutrophils were also pretreated with dinitrofluorobenzene, a compound that binds amino groups and can be expected to react with proteins on the cell membrane. In these experiments, the chemiluminescence induced by opsonized zymosan and the pronounced spike of activity produced by the addition of a chemoattractant were completely abolished. These results suggest that the polymorphonuclear leukocyte chemiluminescence response to chemoattractants is mediated by cell surface proteins. Thus, chemoattractants may have a dual role in the acute inflammatory response: (i) the initiation and maintenance of directed cell movement, and (ii) enhancement of metabolic steps mediated at the cell membrane, resulting in microbicidal activity.