Figure 7. T-bet⁺ T_FH cells are required for GC robustness, but dispensable for switching to IgG2c.

Lethally irradiated Tcrb^−/−Tcrd^−/− mice were reconstituted with bone marrow cells from Tcrb^−/−Tcrd^−/− mice and either Bcl6^+/+Tbx21-Cre or Bcl6^f/fTbx21-Cre mice mixed at a 4:1 ratio. After reconstitution mice were infected with 50 TCID₅₀ influenza (PR8). Mediastinal lymph nodes were and analyzed 14 days post-infection. (A) Schematic for bone marrow chimera generation. (B and C) Frequencies (B) and numbers (C) of CD4⁺CD44⁺PD-1^HiCXCR5^Hi T cells. (D) Numbers of NP tetramer⁺CD4⁺CD44⁺ T cells. (E) Percent of GL7⁺Fas⁺ of total B cells. (F) Numbers of GC B cells (B220⁺GL7⁺Fas⁺). (G) Numbers of HA⁺ GC B cells (B220⁺GL7⁺Fas⁺HA⁺). (H) Percent IgG2c⁺ of GC B cells (B220⁺GL7⁺Fas⁺). (B to H) Each point represents an individual mouse with mean ± s.e.m. All data are representative of ≥ 2 experiments, n ≥ 11 mice per group. Two-tailed t-test (***P < 0.001, **P < 0.01, *P< 0.05, and NS = not significant).