Figure 2. Aicda^GV/GV B cells do not undergo CSR at homeostasis or during acute viral infection.

(A-D) Homeostatic class switch recombination (CSR) in secondary lymphoid organs. Representative gates of IgG1 (A) or IgA (B) class-switched B cells in mesenteric lymph node (LN) (A) or Peyer’s patch (B) germinal centers (GC) (IgG1⁺ or IgA⁺ of GL7⁺Fas⁺ B220⁺ live cells). Quantification of class-switched B cells within the mesenteric LN (C) or Peyer’s patch GCs (D). (E-J) CSR in response to influenza A virus infection. Mice were intranasally infected with 50 TCID50 PR8 or J1 and analyzed at d21 post-infection. (E) Representative gates showing hemagglutinin-specific (HA⁺) GC B cells (HA⁺ of GL7⁺Fas⁺B220⁺ live cells) in the mediastinal LN. Quantification of HA⁺ frequency within GC B cells in the mediastinal LN (F) or spleen (G). Representative gates showing IgG1⁺ and IgG2c⁺ (H) or IgD⁻IgM⁻ and IgM⁺ (I) B cell populations in mediastinal LN GC HA⁺ cells (IgG1⁺, IgG2c⁺, IgD⁻IgM⁻, or IgM⁺ of HA⁺GL7⁺Fas⁺B220⁺ live cells). (J) Quantification of HA⁺ class-switched B cells within mediastinal LN GCs. Data in (A-D) are from 2 independent experiments with 3–6 mice per genotype, (E-J) are from 5 independent experiments with 2–8 mice per genotype. Aicda^GV/GV, Aicda^G133V/G133V. Error bars represent the mean ± std. dev. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001; ns, not significant, p ≥ 0.05. (C,D) all comparisons p < 0.0001 unless noted; (J) all comparisons p < 0.05 unless noted. p-values calculated using a one-way ANOVA with Tukey’s multiple comparisons test without pairing.