The relationship between luminol chemiluminescence and killing of staphylococcus aureus by neutrophil granulocytes

Luminol chemiluminescence induced by phagocytosis of bacteria was studied in a system consisting of polymorphonuclear granulocytes (PMN), serum, luminol and Staphylococcus aureus. To evaluate the quantitative relationship between luminol chemiluminescence and the bactericidal process time courses for both variables were compared. It was found that initial rate of increase of chemiluminescence and initial rate of killing of bacteria were well correlated whereas the correlation was poorer for later stages of the process. When the rate of the bactericidal process was varied by changing concentrations of bacteria and PMN, directly proportional variations of initial rates of increase of chemiluminescence were observed. This is interpreted as reflecting an accumulation of oxidizing radicals as the result of a phagocytosis dependent gradual activation of the NADPH oxidase system, leading to luminol oxidation and/or killing of bacteria. However, by thermal inactivation of PMNs, chemiluminescence could be diminished whereas killing remained essentially unaffected, showing that these two processes could be uncoupled. Also, addition of erythrocytes to the PMN suspension was associated with decreased chemiluminescence and lysis of erythrocytes with an increased chemiluminescence, emphasizing the importance of proper control of the components of the leucocyte test suspension.