Intracellular calcium rises in synchrony with PMN arrest and polarization. (A) Data for human PMNs responding to fMLP stimulation are compiled from more than 200 individual observations onto 1 plot to compare the dynamics of calcium, arrest, and polarization. Arrest is represented here as the fraction of cells remaining rolling (ie, the inverse of arrest). (B) Data for human PMNs treated with thapsigargin and stimulated by the addition of 1.5mM CaCl₂ are also compiled onto 1 plot to compare the dynamics of calcium arrest and polarization. Arrest is represented as in panel A. (C) Human and mouse PMNs were loaded with fluo-5f, perfused over a glass coverslip coated with recombinant E-selectin-Fc and ICAM-1-Fc, and imaged by TIRF microscopy. Representative images from 3 separate experiments are indicated. (D) Calcium (fluo-5F) intensity over 60 seconds, untreated PMNs had significantly higher relative fluo-5f signal than 2-APB treated cells at 15 seconds and higher time points (P < .01). (E) Calcium (fluo-5F) signal in mouse WT versus Orai1−/+ PMNs over 60 seconds. **P < .01. ***P < .001. Error bars represent the SE for each measured time point.