Calcium influx of splenic B cell. The calcium influx in splenic B cells was examined by FACS. The Sfrp2+/+ and Sfrp2-/- splenic B cells were derived from 3 littermates with same gender pair and assessed after gated with anti-B220. The means of 3 replicates are plotted by the blue circles (Sfrp2+/+) and red squares (Sfrp2-/-). The black asterisks indicate the statistical significance by paired t-test in each time point. Blue shaded regions indicate the differences of intensity ratios between Sfrp2+/+ and Sfrp2-/- splenic B cells. (A) After 1.5 min acquisition of signals, the cells were stimulated with anti-IgM (IgM; open arrow). Furthermore, the cells were treated with calcium at 3 min (dotted arrow). (B) Following the similar process, the cells were then incubated with EGTA at 7 min (filled arrow).