S. flexneri induces B cell death dependent on the T3SA in vivo. (A) Total cell count in murine LNs after footpad infection with S. flexneri. Cells were counted 24 and 48 h after WT and T3SA⁻ infection. (B) Percentages of CD19⁺ B cells in murine popliteal LNs 24 and 48 h after footpad infection. (C) Percentages of PI⁺ CD19⁺ B cells in murine popliteal LNs 48 h after footpad infection. (D) Percentages of CD4⁺ T cells in murine popliteal LNs 48 h after footpad infection. (E) Number of CFUs for WT and T3SA⁻ bacteria in murine LNs 48 h after footpad infection. Two independent experiments with each 5 mice per group (10 LNs) were performed and data are presented as mean ± SEM. Asterisks indicate statistical significant differences between WT and T3SA⁻, determined by Mann-Whitney Student’s t test. *, P < 0.05; **, P < 0.01; ***, P < 0.001.