Supplementary Figure 2: Persistent protective response and GC-independent IgG2 memory B formation in Bcl6-deficient mice.

(a) Naive mice were intravenously treated with sera from WT, or Bcl6^ΔT mice collected at 2 weeks or 1 year after vaccination and then infected with a lethal dose of Narita (2.5 LD₅₀/mouse). Body weight was measured in the mice receiving sera from the unvaccinated C57BL/6 mice (UV) (closed circle), the WT mice at 2-week (2wk) (open circles) (n=5) and 1-year (1y) (filled blue circle) (n=4) post vaccination, and Bcl6^ΔT mice at 1-year post vaccination (filled red circles) (n=4). Statistical analysis was performed using Mann-Whitney U test. **P<0.01. *P<0.05. (b) Circles represent IgG2b⁺ B cell number of HA binding CD38⁺ memory cells and GL-7⁺ GC B cells. (c and d) The memory B cells were transferred into Rag1-deficient mice with Narita primed T cells. Circles represent the frequency of virus-specific IgG2b (c) and IgG2c (d) in the spleen at day 7 after IAV challenge (n = 4).