Mobilization of intracellular calcium induced by AAT. Neutrophils loaded with the fluorescent Ca2+ indicator Fluo-3 were measured flow cytometrically in a buffer without Ca2+ containing 1 mmol/L EGTA. Fluo-3 fluorescence of neutrophils was measured for 20 s on unstimulated cells before the injection of AAT at various concentrations (arrows). After addition of AAT, measurement was continued until a total time of 100 s. (A) Fluo-3 fluorescence of single cells (gated on neutrophils on the basis of scatter properties) was plotted against time. The black curve indicates the median fluorescence of neutrophils. AAT (1 mg/mL) addition is marked by the arrow. (B) Comparison of Ca2+ kinetics after stimulation with various concentrations of AAT.