Figure 5. BCR-mediated Ca²⁺ entry in DT40 cells.

WT (A) and GFP-IP₃R3-transfected IP₃R-KO (B) cells were stimulated with anti-IgM in nominally Ca²⁺-free medium, and La³⁺ (0.3 μM) and Ca²⁺ (1.3 mM) were subsequently added. (A) (a) Fluorescence image of fura 2; (b–d) pseudocolour images of fura 2 ratio obtained at time points indicated in (e); (e) time-dependent changes in the fluorescence ratio in the cells depicted in the fluorescence image (a). (B) (a) Merged fluorescence image of GFP-IP₃R3 and fura 2; (b–d) pseudocolour images of fura 2 ratio obtained at time points indicated in (e); (e) time-dependent changes in the fluorescence ratio in the cells depicted in the fluorescence image (a). GFP-IP₃R3-expressing cell is indicated by an arrow. The horizontal bars at the top of the Figure indicate the presence of anti-IgM, La³⁺ and Ca²⁺. The ratio is presented as relative fluorescence intensity (F₃₄₀/F₃₈₀). Scale bar, 10 μm. (C) La³⁺-insensitive Ca²⁺ entry was monitored in WT-DT40 cells and GFP-IP₃R3-transfected IP₃R-KO cells. The number of cells showing La³⁺-insensitive Ca²⁺ entry in the absence (−) and presence (+) of anti-IgM was quantified and plotted as a percentage of the total number of cells. Total number of cells counted is shown above each column.