FcϵRI-but not thapsigargin-induced Ca²⁺ responses are faster in cell lines expressing catalytically inactive PLD1. Cells were stimulated at the time indicated by the arrow with antigen (100 ng/mL) or thapsigargin (100 nM). Experiments were in the presence (+Ca²⁺) or absence (-Ca²⁺) of extracellular Ca²⁺. The graphs shown are the Ca²⁺ response of 10 individual cells for each cell line (faint lines), representative of the 60 cells within each experiment, and the average of the 60 cells (thick line in antigen stimulation). The result shown is representative of 3 independent experiments, and similar results were obtained when the other cell line of each transfection was examined.