Impaired plasma cell differentiation in Stat1^−/− MZ B cells in response to TLR stimulation. MZ B cells of WT and Stat1^−/− mice were stimulated with 1 µg/ml CpG (A) and 2 µg/ml LPS (B), respectively, for 2 d, stained with antibodies to B220 and CD138, and analyzed by flow cytometry. One experiment out of three is shown. (C) The mean percentages of plasma cell (B220⁻CD138⁺) after stimulation are shown (n = 3). Results represent three experiments. MZ B cells were stimulated with 1 µg/ml CpG for 3 d, and then subjected to ELISPOT assay. (D) The spots of ASCs are shown. One experiment out of three is shown. The frequencies of ASCs per 10³ MZ B cells (E) and mean area of each spot (F) in the ELISPOT assay is shown (n = 3). Results represent three experiments. Same as in B, except mRNA was prepared from the cells before and after stimulation with LPS and subjected to RT-QPCR using primers to Pax5 (G), Bcl6 (H), Prdm1 (I), and Xbp1s (J). All genes were normalized to Rpl7 (n = 4). Results represent two experiments. All values are shown as the means ± SD. *, P < 0.05; **, P < 0.01, Student’s t test.