Overexpression of Bcl-2 rescues the antibody defect in SFR KO mice. (A and B) Mice were immunized with NP-OVA, and on day 9, expression of Bcl-2 in NIP⁺CD19⁺GL7^hi cells was analyzed. A sample plot is shown in A, and mean fluorescence intensities (MFIs) of Bcl-2 in multiple mice are shown in B (WT, n = 6; KO, n = 9). Data are pooled from two experiments. (C–G) WT and SFR KO mice were bred or not with mice overexpressing a transgene encoding human Bcl-2. Mice were then analyzed as outlined in C. NIP⁺IgM⁺ and NIP⁺IgG1⁺ GC B cells were enumerated in spleen (D), while anti-NP IgG1 was measured in serum (E). Numbers of total CD19⁺CD95⁺GL7^hi GC B cells (F) or Tfh cells and GC Tfh cells (G) were determined. In E, statistics are provided for SFR KO versus SFR KO Bcl-2^Tg and for WT versus SFR KO Bcl-2^Tg. For D, F, and G, WT, n = 4; WT Bcl-2^Tg, n = 3; SFR KO, n = 7; and SFR KO Bcl-2^Tg, n = 8. For E, WT, n = 6; WT Bcl-2^Tg, n = 6; SFR KO, n = 14; and SFR KO Bcl-2^Tg, n = 9. Data were pooled from three experiments. Each symbol represents one mouse. *, P < 0.05; **, P < 0.01; ****, P < 0.0001 (two-tailed Student’s t test). Data are shown as mean ± SEM. D, day; ns, not significant; Tg, transgene.