Figure 5. ICOS → Bcl6 → CXCR5.

(A–E) Blimp1 expressing (Prdm1-RV⁺, GFP⁺) and non-transduced (GFP) SM CD4⁺ T cells were transferred into the same (A) or separate (B–E) B6 recipient mice. (A) SM CD4⁺ T cells at day 4 after LCMV infection. (B) WT SM vs. Prdm1-RV⁺ SM CD4⁺ T cell expansion (% of total CD4⁺ T cells). (C, D) CXCR5 expression by Prdm1-RV⁺ SM and WT SM, day 4 p.i. (C) Representative FACS plots showing WT (GFP) and Prdm1-RV⁺ (GFP⁺). Gates identify CXCR5⁺Bcl6⁺ SM. (D) Quantitation of CXCR5⁺ and CXCR5⁺Bcl6⁺ SM. (E) CXCR5⁺ SM and Bcl6⁺CXCR5⁺ Tfh cell frequencies day 3 p.i. (F, G) Bcl6 shRNA-RV⁺ (GFP⁺Ametrine⁺) and non-transduced (GFP⁻Ametrine) SM CD4⁺ T cells were transferred into separate B6 recipient mice subsequently infected with LCMV. (F) SM CD4⁺ T cell expansion, day 4 p.i. (% of total CD4⁺ T cells). (G) Representative FACS plots of CXCR5 and Bcl6 expression by WT SM and Bcl6 shRNA⁺ SM CD4⁺ T cells. Total SM cells are shown and gates identify Bcl6⁺CXCR5⁺ SM. Data are representative of three (A–E) and two (F–G) independent experiments; n = 4 per group per time point. **P<0.01, ***P<0.001.