Effect of Stim1/2 ablation on the ultrastructure of mouse neutrophils. (A) Representative electron micrographs of suspended (top) and adherent (bottom) neutrophils purified from WT (left) and Stim1/2^KO (right) mice. Arrowheads indicate ER structures located <35 nm from the PM at unsettled (black) or adherent (white) membranes. Ѳ: adjacent cell. Scale bar: 1 µm. Insets: Higher magnification micrographs showing cER sheets (asterisks) apposed to the PM (closed circle). Black arrow denotes the dish bottom. Scale bar: 40 nm. Micrograph of adherent Stim1/2^KO neutrophil is replicated in Fig. 7 A. (B) Percentage of PM decorated by cER and quantification of cER length and ER-PM gap distance in suspended (Susp) and adherent (Adh) WT and Stim1/2^KO neutrophils. n = 15/15 Susp, 26/19 Adh cells with 148/95 cER sheets and 150/124 cER sheets from two mice pairs, Mann–Whitney U test. (C) Percentage of adhesive membrane with cER. n = 26/19 cells. Lines show median values, larger symbols mouse average.