PULSATILE CA2+ INFLUX IN HUMAN NEUTROPHILS UNDERGOING CD11B CD18 INTEGRIN ENGAGEMENT/

Rapid-time confocal scanning has demonstrated that neutrophils undergo ing CD11b/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+ concentrati on at the start of the influx. Influx events occurring less than 100 s econds after the previous Ca2+ rise were observed not to reach the con centration of the preceding peak, whilst events occurring later usuall y exceeded the magnitude of the previous Ca2+ concentration. This sugg ested temporary inactivation, followed by recovery, of the Ca2+ influx mechanism. In addition, Ca2+ influx was most likely to occur immediat ely following this recovery. The involvement of Ca2+ store release at the site of integrin engagement suggested that the cytoskeletal connec tion between the peripheral store and membrane was facilitating the si gnalling of Ca2+ influx. (C) 1997 Academic Press