Fig. 5. Microbial stimuli fail to induce an acute Ca²⁺ flux. Macrophages were loaded with Fura-2 and used for live cell Ca²⁺ imaging. (A, left panel) Fura-2-loaded macrophages were treated with thapsigargin (thg; 1 µM) after 3 minutes of baseline recording to demonstrate a typical Ca²⁺ response in these cells. Live T. gondii (A, right panel; 5:1), STAg (B; 50 µg/ml) or LPS (C; 100 ng/ml) was added to Fura-2-loaded macrophages following 3 minutes of baseline recording (arrows) and intracellular Ca²⁺ was recorded over the time period indicated. At the end of experiments in B and C, thapsigargin (thg; 1 µM) was added to demonstrate a positive response. Individual lines in each panel represent the intracellular Ca²⁺ level within each individual cell in the imaging field expressed as a 340/380 ratio. Experiments typically included 55-65 cells per imaging field. Recordings are representative of five to seven experiments for each condition.