Abolished Ca²⁺ influx in the patient’s EBV-B cells is restored by expression of STIM1. (A) EBV-B cells of the patient (P) and two controls (C1 and C2) were stimulated with 1 µM thapsigargin (TG) in Ca²⁺-free Ringer solution (open bars) followed by perfusion with 2 mM Ca²⁺ (filled bars) to induce Ca²⁺ influx. Traces represent mean F340/F380 emission ratios of one representative experiment. Averages on the right are from n = 6 (C1), n = 4 (C2), n = 5 (P) experiments. ΔF340/F380 represents peak [Ca²⁺]_i 25 s after readdition of Ca²⁺ minus baseline [Ca²⁺]_i at the beginning of the recording. Error bars represent the SEM. ***, P < 0.0001. (B) EBV-B cells from the patient were retrovirally transduced with STIM1-IRES-GFP expression vector (P-STIM1) or ORAI1-IRES-GFP vector (P-ORAI1). Ca²⁺ levels were measured as described in A. Traces of individual cells (thin gray lines) and averages of all cells (thick black lines) are shown for 90 GFP⁺ and 90 GFP⁻ cells. Averages of peak ΔF340/F380 from total 368 cells (P-STIM1; n = 6 experiments) or 482 cells (P-ORAI1; n = 10 experiments) are shown in the bar graph. Error bars represent the SEM. ***, P < 0.0001; ns, P > 0.05.