Development and TLR-induced activation, proliferation, and apoptosis of Stat1^−/− MZ B cells are normal. (A) Splenocytes of WT and Stat1^−/− mice were stained with antibodies to B220, CD21, and CD23, gated on B220, and analyzed for MZ B cells (B220⁺CD21^hiCD23^lo) by flow cytometry. One experiment out of three is shown. (B) Mean numbers of WT and Stat1^−/− MZ B cells are shown (n = 4–9). Results represent three experiments. (C–F) MZ B cells of WT and Stat1^−/− mice were stimulated with 1 µg/ml CpG (C and D) or 2 µg/ml LPS (E and F) for 24 h, stained with antibodies to CD69 (C and E) and MHC class II (D and F), respectively, and analyzed by flow cytometry. One experiment out of two is shown. (G and H) Same as in C–F, except the culture supernatant of the stimulated cells were subjected to ELISA for measuring the production of IL-6 (G) and IL-10 (H) before and after the treatments (n = 2). Results represent two experiments. (I) Same as in A and B except cells were stimulated for the indicated times, pulsed with BrdU for the last 2 h, and stained with anti–BrdU-FITC, and then BrdU incorporation measured by flow cytometry. One experiment out of two is shown. (J) Same as in I except the cells were treated for the indicated times, stained with Annexin V, and analyzed with flow cytometry (n = 3). Results represent three experiments. All values are shown as the means ± SD. *, P < 0.05, Student’s t test.