Figure 4. Pbx1-d Tg expression in CD4⁺ T cells regulated Ag-specific T_FH cell differentiation.

T_FH cells were analyzed 5 d after NP-OVA immunization of CD45.1⁺ B6 mice transferred with CD45.2⁺ naïve B6.OT-II or Pbx1-d Tg.OT-II cells. A. Representative flow cytometric plots showing mLN CD4⁺ CD45.1⁺ (endogenous) and CD45.2⁺ (transferred) gated CXCR5⁺PD-1⁺ T_FH and T_FR cells. B. Percentages of donor and recipient T_FH cells. C. Absolute numbers of donor T_FH cells. Each symbol represents a recipient mouse. D. Localization of donor OT-II CD4⁺ T cells (CD45.2⁺, red) relative to B cell follicles (IgD⁺, F), GCs (GL7⁺, green), and periarteriolar lymphoid sheaths (PALS). The framed areas in the 10x magnification are shown below at 20x, with the bottom panels showing only the outline of the IgG⁺ B cell follicles for a better comparison of the number and location of CD45.2⁺ T cells. E. Numbers of B6.OT-II or Pbx1-d Tg.OT-II CD4⁺ T cells in B or T cell zones, showing mean ± SEM from 3–7 GC regions per mouse from 3 mice per strain. F. Percentages of donor and recipient T_FH cells 5 d after NP-OVA immunization of CD45.1⁺ B6 mice transferred with CD45.2⁺ naïve B6.OT-II or Sle1a1.OT-II cells. G. Representative 20x spleen sections of B6.OT-II or Sle1a1.OT-II cell recipients, as in D. H. Numbers of B6.OT-II or Sle1a1.OT-II CD4⁺ T cells in B or T cell zones, showing mean ± SEM from 3–7 GC regions per mouse from 5 mice per strain. *P < 0.05, **P < 0.01.