BCL6 is elevated in steady-state cDCs.

<p><i>(A)</i> Splenocytes from naïve C57BL/6 mice were stained for cDCs subsets or pDCs, and for intracellular BCL6 protein expression. Representative FACS plots were shown (n = 8): Isotype controls (solid grey), BCL6 expression of GC B cells gated as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101208#pone-0101208-g001" target="_blank">Figure 1</a> as positive controls (dashed line), BCL6 expression of the indicated DC population (open black). BCL6 expression gates were drawn based on the negative expression of isotype controls, and the percentage of BCL6⁺ cells of the gated cDC population indicated. <i>(B)</i> Representative immunofluorescence picture shows the staining pattern of CD11c (red), BCL6 (green), B220 (blue), and MOMA-1 (grey). Solid white arrows identify CD11c⁺ cells expressing BCL6 with higher intensity, and open white arrows indentify CD11c⁺ cells expressing BCL6 with lower intensity. <i>(C)</i> Mean fluorescence intensity (MFI)±SEM (n = 4) of CD11c (left panel) and I-A/E (right panel) in either BCL6^hi (solid bar) or BCL6^lo (open bar) cDCs. <i>(D)</i> BM and splenic pre-cDCs, spleen cDCs, and naïve B cells were sorted from naïve C57BL/6 mice; control GC B cells and T follicular helper (T_FH) cells were sorted from immunized mice as described in the methods section. Bcl6 transcript levels were determined by quantitative RT-PCR. Normalized expression is relative to the corresponding β-actin control. Bar Graph shows the relative expression ± SEM (n = 3) of Bcl6 in different DC populations and control cells. *<i>p</i><0.05; **<i>p</i><0.005; ***<i>p</i><0.001 (students T-test) as compared to Bcl6 transcripts in Naïve B cells.