The kinetics of BrdU labeling in WT and Spi-B–deficient pDCs. Mice were injected intraperitoneally at day 0 with BrdU and given BrdU continuously in the drinking water. At the indicated days, BM and spleen cells were analyzed for BrdU incorporation. The percentages of CD19⁻CD11c⁺B220⁺BST2⁺ cells (ie, pDCs) among total cells are shown. BrdU⁺ and BrdU⁻ cells among the pDCs are indicated by black and white columns, respectively (4 mice at each time point, means ± SD). Each symbol represents the data from one mouse and the bars indicate the mean. **P < .01.