Figure 6. Representative Ca²⁺ signaling images in the spleen of autoimmune-prone YC3.60^flox/CD19-Cre/CD22^−/− and YC3.60^flox/CD19-Cre/lpr/lpr mice.

(a) Images of Ca²⁺ signaling in the spleen of a YC3.60^flox/CD19-Cre/CD22^−/− mouse. Representative Ca²⁺ images based on the ratio (YFP/CFP at excitation of 458 nm) at indicated time points are shown. Cells exhibiting FRET signals are indicated by arrows. Results are representative of at least three independent experiments (n > 3 mice). (b) Time courses of intracellular Ca²⁺ fluxes. Ratiometric intensities (YFP/CFP at excitation of 458 nm) of indicated cells in (a) were measured every 5 s for 5 min. (c) Ratiometric intensities (YFP/CFP on excitation at 458 nm) of splenic B cells from wild-type and CD22^−/− mice. Bars denote mean values. P < 0.01 (t-test). n = 50. (d) Distribution of time-integrated intracellular Ca²⁺ concentrations of B cells. Percentages of ratio > 1.2 were indicated. n = 50, frame = 61. (e,f) Representative Ca²⁺ signaling images in the spleens of YC3.60^flox/CD19-Cre /lpr/lpr mice. (e) Images of Ca²⁺ signaling in the spleen of a YC3.60^flox/CD19-Cre/lpr/lpr mouse. Representative Ca²⁺ images based on the ratio (YFP/CFP at excitation of 458 nm) at indicated time points are shown. (n = 3 mice). (f) Mean ratio (YFP/CFP at excitation of 458 nm) of splenic B cells from YC3.60^flox/CD19-Cre and YC3.60^flox/CD19-Cre/lpr/lpr mice. Bars denote mean values. P < 0.01 (t-test). n = 50. (g) Distribution of time-integrated intracellular Ca²⁺ concentrations of B cells. Bars denote mean values. n = 15, frame = 48.