Elevation of extracellular calcium rescues the endocytosis defect in Flower-deficient CTLs. (A) Time-lapse maximal-intensity projections of syb2-mRFP (red) transfected CTLs in contact with target cells before and after application of extracellular buffer containing 10 mM calcium. CTLs were incubated with target cells in the presence of anti-RFP488 antibody (green) in the medium for 30 min and then perfused with 10 mM calcium buffer. Bars, 10 µm. (B) Quantitative analysis of the accumulation of endocytic CGs at the IS (one third of CTL volume projecting toward the target cell) over time from panel A. Time zero is defined as the appearance of the first endocytic CG at the IS. Data are given as mean ± SEM; unpaired Student’s t test: ***, P < 0.001.