Bcl6 controls generation of GC Tfh, but not cytokine profile, in responding effector cells.

<p>(A) Naïve (CD44^loCD25^-) CD4 T cells (2x10⁶) from either Bcl6^fl/fl CD4^Cre (Bcl6 cKO) or Bcl6^fl/fl (WT) were labeled with cell trace violet (CTV) and adoptively transferred into Ly5.1 (CD45.1) congenic mice, followed by <i>P</i>. <i>chabaudi</i> infection. On day 7 post-infection, splenocytes were harvested and stained with (B) CD4, CD45.2, CTV, (C, D) PD-1, CXCR5, (E) IFN-γ, IL-21, and (F) IFN-γ, IL-10. (B) Plots showing the gating on responding CD4⁺CD45.2⁺CTV^- T cells. (C) Graph shows percentages for individual recipients of effector T cell subsets. No CD45.2⁺ CXCR5^hiPD-1^hi GC Tfh cells were detected in any recipient of Bcl6 cKO T cells. (D) Bar graph shows CXCR5 MFI of CD4⁺CD45.2⁺CTV^- donor cells. (E) Plots and bar graph of average IFN-γ and IL-21 cytokine producers in the responding donor cells (CD45.2⁺CTV^-) in recipients of WT and Bcl6 cKO T cells. (F) Dot plot showing intracellular cytokine staining. Data are representative of three independent experiments with 4–5 animals per group. Numbers within plots represent mean percentages. Statistical significance was obtained using Students <i>t</i>-test. Error bars represent the SEM; ^★<i>p</i> < 0.05, ^★★★<i>p</i> < 0.001, ns = not significant.