Increased percentages of CD62L ⁺ Tfh cells during the progression of immune responses. (A and B) Kinetic expression of PD-1 and CD62L in CD4⁺CD44^hiCXCR5⁺Bcl6⁺ GC-Tfh cells after KLH immunization at indicated time points. (C) The ratios of PD1⁺ versus CD62L⁺ Tfh cell percentages at indicated time points. (D and E) Kinetic expression of PD-1 and CD62L in adoptive-transferred CD45.1⁺CD44^hiCXCR5⁺Bcl6⁺ OT-II T cells after OVA immunization at indicated time points. (F) The ratios of PD1⁺ versus CD62L⁺ cell percentages in transferred CD45.1⁺CD44^hiCXCR5⁺Bcl6⁺ OT-II T cells at indicated time points. (G) Representative Bcl6 intracellular staining levels in PD-1⁺, CD62L⁺ Tfh cells, and non-Tfh cells at indicated time points. (H) Mean fluorescence intensities (MFI) of Bcl6 expression in CD62L and PD-1⁺ Tfh cells at each time point. (I) Chromatin accessibility of the Bcl6 gene locus of CD62L⁺ Tfh, PD-1⁺ Tfh, and naïve CD4⁺ T cells were analyzed in parallel. Red lines highlight the differentially accessible regions of Bcl6 gene within different cells. Data of A–G represent two independent experiments. Data are shown as mean or mean ± SD; two-tailed t test; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, no significance.