Fig. 2. Single-cell intracellular calcium imaging on iDCs. (A,C) Single-cell intracellular calcium measurements in fura-2-loaded iDCs obtained after 5 days of culture. The traces show changes in fura-2 fluorescence ratio (340/380 nm) in a single iDC after addition of caffeine or ATP. Experiments were performed in Krebs-Ringer containing 1 mM Ca²⁺. (B,D) Average peak increases in fluorescence ratio induced by the addition of the indicated agonists to fura-2-loaded iDCs. Results represent the mean increase in fluorescence (calculated by subtracting the peak fluorescent ratio from the resting fluorescent ratio) obtained after addition of 600 µM 4-chloro-m-cresol, 10 mM caffeine or 150 mM KCl (B) or 100 µM ATP (D). No difference was found in the peak Ca²⁺ in response to RyR activation (P=0.820), but the amount of Ca²⁺ released by 100 µM ATP was significantly higher (P<0.00001). Results represent the mean (± s.e.m.) increase in fluorescence in DCs isolated from four different donors.