Influence of pH and temperature on the luminol-dependent chemiluminescence of human polymorphonuclear leucocytes

Human polymorphonuclear leucocytes were stimulated with the chemotactic peptide N-formylmethionyl-leucyl-phenylalanine and the luminol-dependent chemiluminescence produced was measured as a function of pH in the interval 6.85-7.70 and as a function of temperature in the interval 21-37 degrees C. The time response of the chemiluminescence signal after addition of the peptide consisted of two peaks at 21 degrees C. The separation in time between the maxima of the two peaks and the width of the second peak decreased with increasing temperature. The two peaks coalesced at 37 degrees C. The intensity of the initial peak showed a strong pH dependence, whereas the second peak was rather insensitive to pH changes. The results point to the importance of a rigorous control of pH and temperature if quantitative luminol-dependent chemiluminescence measurements are to be made. The results of this work also support the view that the initial peak originates from reactions taking place at the outside of the cell and that the second peak is caused by intracellular reactions.