Fig. 1. (A , B ) Caffeine (25 and 50 mm)-induced Ca²⁺responses in B cells from malignant hyperthermia-susceptible (MHS) (closed squares) and control individuals (open squares). Two sets of experiments (A , B ) from four unrelated individuals are shown. Changes in [Ca²⁺]ⁱin B cells were analyzed as percent increase of fluo-3⁺cells relative to the base line established by standard calibration (% fluo-3⁺). The percent increase of fluo-3⁺cells in CD19⁺B cells was monitored using flow cytometry as described in Materials and Methods . Plotted are mean % fluo-3⁺cells of 500 to 1,000 CD19⁺B cells at each time point. (C ) The 4-chloro-m-cresol (4CmC) (100, 200, and 400 μm)-induced Ca²⁺responses in CD19+ B cells. Data were expressed as the mean ± SEM of Delta % fluo-3⁺cells from MHS (filled bars, n = 6 at 100 μm, 8 at 200 μm and 12 at 400 μm), malignant hyperthermia-negative (MHN) (hatched bars, n = 8 at 100 μm, 13 at 200 μm and 21 at 400 μm) and control individuals (open bars, n = 8 at 100 μm, 9 at 200 μm and 18 at 400 μm). Delta % fluo-3⁺cells were calculated as peak % fluo-3⁺cells-basal % positive cells. Repeated measures analysis of variance (RM ANOVA) revealed significant differences between the groups at 200 μm (*P = 0.042) and 400 μm (**P = 0.010).