Activation of human neutrophil metabolism by streptolysin O

The effect of streptolysin O on the metabolic activity of human neutrophils was examined. Streptolysin O, within the range of 3 to 75 hemolytic units, stimulated neutrophils to emit light. This chemiluminescence was the result of metabolic activation, as confirmed by oxygen uptake studies and the suppression of chemiluminescence by the metabolic inhibitor, 2-deoxyglucose. Free cholesterol, which prevents streptolysin O from binding to membrane cholesterol, blocked the neutrophil chemiluminescent response to streptolysin O. Extracellular calcium ions were necessary for the streptolysin O-stimulated chemiluminescent response of neutrophils. Some cell viability was lost, as measured by trypan blue uptake and neutrophil lysis within the range of streptolysin O concentration that caused metabolic stimulation. These observations suggest a possible role for streptolysin O as a pathogenic factor in streptococcal infections.