Pulsatile Ca2+ influx in human neutrophils undergoing CD11b/CD18 integrin engagement

Rapid-time confocal scanning has demonstrated that neutrophils undergoing CDllb/CD18 integrin-dependent adhesion show repeated elevations in cytosolic free Ca2+ concentration, due to Ca2+ influx. The magnitude of each individual influx, compared to the previous one, depended upon the time between the two, and not upon the cytosolic Ca2+ concentration at the start of the influx. Influx events occurring less than 100 seconds after the previous Ca2+ rise were observed not to reach the concentration of the preceding peak, whilst events occurring later usually exceeded the magnitude of the previous Ca2+ concentration. This suggested temporary inactivation, followed by recovery, of the Ca2+ influx mechanism. In addition, Ca2+ influx was most likely to occur immediately following this recovery. The involvement of Ca2+ store release at the site of integrin engagement suggested that the cytoskeletal connection between the peripheral store and membrane was facilitating the signalling of Ca2+ influx.