Figure 3. T_FR cells express Bcl-6 and Blimp-1.

(a) Bcl6 and Prdm1 mRNA normalized to Gapdh determined by quantitative RT-PCR from sorted cells using the strategy described in Fig. 1d and Supplementary Fig. 1. Heights of the bars represent the mean and error bars represent the range of expression from 3 biological replicates. Statistical significance was determined using a one-way ANOVA analysis with Bonferroni’s multiple testing correction; * P<0.05; **P<0.01; ***P<0.001. Bar graphs are representative of 3 experiments. (b) Immunofluorescence of frozen spleen sections from mice immunized seven days previously with SRBC. The germinal center is demarcated by the white dotted line in the three consecutive sections. Upper panel: AID (red) and CD3 (green); middle panel: Foxp3 (red) and Bcl-6 (green); lower panel: Foxp3 (red) and Blimp1 (green). Scale bar represents 100μm. (c) Flow cytometric contour plots of T_FH (upper panels) & T_FR (lower panels) formation in the draining (mediastinal) lymph node ten days after intranasal influenza infection of mixed fetal liver chimeras reconstituted with a 1:1 ratio of fetal liver cells from E14.5 CD45.2 Prdm1^gfp/gfp : CD45.1 Prdm1^+/+ embryos, E14.5 CD45.2 Bcl6^−/− : CD45.1 Bcl6^+/+ embryos or control E14.5 CD45.2 Prdm1^gfp/+ : CD45.1 Prdm1^+/+ embryos.