Figure 1.

Mice lacking follicular regulatory CD4⁺ T cells have reduced antigen-specific GC responses. Analysis of the GC B cell responses in Bcl6^f/f and Bcl6^f/f Foxp3-Cre mice at the late time point following influenza virus infection. (A) Left: Representative plots of the GC B cell responses in Bcl6^f/f or Bcl6^f/f Foxp3-Cre mice at day 38 p.i. Right: Frequency and number of cells as indicated by the gates shown on the left. (B) Representative confocal images of the GCs from Bcl6^f/f or Bcl6^f/f Foxp3-Cre mice at day 36 p.i. IgD shown in blue and peanut agglutinin shown in red. Right: GC sizes as measured by ImageJ. Scale bar, 100 µm. (C) Left: Representative plots of HA-specific GC B cells at day 38 p.i. The cells were gated on GL7⁺ CD38⁻ GC B cells of the B220⁺IgM⁻IgD^low population. Right: Frequency and absolute numbers of HA-specific GC B cells. (D) RNA-seq analysis of HA⁺ GC B cells from Bcl6^f/f and Bcl6^f/f Foxp3-Cre mice at 36 d following influenza virus infection. Volcano plot of -log₁₀ P value vs. log₂ fold change of the most differentially expressed 5,000 genes. The dashed line plotted indicates the level of Bonferroni-corrected P value <0.05. No gene is found to show significance change with adjusted P value <0.05. (E) Plaque assay measuring viral load in Bcl6^f/f and Bcl6^f/f Foxp3-Cre mice at day 5 and day 9 p.i. Statistical analyses were performed using the unpaired two-tailed Student’s t test (*, P < 0.05; **, P < 0.01). Data for A and C are from one experiment representative of four experiments with five to seven mice per group. Data for B and E are from one experiment representative of two experiments with three to five mice per group. Data for D are from two independent experiments with three to four mice per group pooled for each sample. n.s., not significant.