Effect of Stim1/2 ablation on actin dynamics at neutrophils adhesion sites. (A) Representative electron micrographs of purified WT and Stim1/2^KO adherent neutrophils (left) and quantification of the organelle-free area (presumably rich in actin) covering their adhesive membranes (right, n = 26/19 cells from two mice pairs, exact two-tailed Mann–Whitney U test). Adhesive (Adh) and nonadhesive membranes are outlined in white and green, respectively, cytosolic pad area in violet. Scale bar: 1 µm. Micrograph of Stim1/2^KO neutrophil is duplicated from Fig. 5 A. (B) Time-lapse micrographs of flushed WT and Stim1/2-deficient neutrophils stained with the cell-permeable F-actin probe SiR-actin (left, Video 10 and Video 11) and change in SiR-actin fluorescence intensity during spreading (right, n = 31/18 cells from 2 WT/Stim1/2^KO mice pairs, exact two-tailed Mann–Whitney U test). Scale bars: 5 µm. AUC, area under the curve.