Figure 3: Resident CD4⁺ T cells are a heterogeneous population including T_FH cells.

(a) Frequency of PD-1^hiCXCR5^hi T_FH cells among CD4⁺CD62L^lo T cells (left) and CD4⁺CD62L^loD-Red⁺ cells (right) in mLN_conv after 7 days (representative of two independent experiments, n=4 mice, mean±s.d.). (b) Frequency of PD-1^hiCXCR5^hi T_FH cells among CD4⁺CD62L^lo T cells (left) and among CD4⁺CD62L^loFITC⁺ cells (right) in PP_inj after 7 days (representative of three independent experiments, n=18 mice, mean±s.d.). (c) Frequency of Foxp3⁺ regulatory T cells for the populations as in a. (d) Frequency of Foxp3⁺ regulatory T cells for the populations as in b. (e) Upper panels: expression of CD62L, CD44, CCR7, IL-7Rα, ICOS and CD69 on all CD4⁺ T cells in PP_inj 7 days after. Lower panels: expression of CD62L, CCR7, IL-7Rα, ICOS and CD69 on CD4⁺CD62L^hi cells (grey-filled histograms), CD4⁺CD62L^loFITC⁻ cells (dashed black lines) CD4⁺CD62L^loFITC⁺ cells (green lines) in PP_inj after 7 days (representative of at least three independent experiments). (f) Frequencies of CCR7⁺, IL-7Rα^hi, ICOS^hi and CD69^hi cells among populations described in e (pooled samples from n=18–24 mice in three to four independent experiments, one-way analysis of variance, Tukey’s post test, *P<0.05; ***P<0.001; not significant (NS)). (g) Histological analysis of D-Red⁺ cells in PP_conv 7 days after photoconversion (GC, germinal center; B, B cell follicle; T, interfollicular T cell area, representative of two independent experiments, scale bar, 50 μm). (h) Frequency of D-Red⁺ and D-Red⁻ cells among all CD3⁺ cells in different areas of PP_conv as in g (six PPs from four mice in two independent experiments, mean±s.d.).