SFR KO mice generate fewer antigen-specific GC B cells, memory B cells, and antibody-secreting cells. (A–G) As in Fig. 2 B, except that NP-specific immune cells were detected by flow cytometry using NIP, an analogue of NP. The protocol is depicted in A. NIP⁺IgD⁻ total B cells (B), NIP⁺IgM⁺ or NIP⁺IgG1⁺ GC B cells (C), NIP⁺IgM⁺ or NIP⁺IgG1⁺ memory (mem) B cells (D), and NIP⁺B220⁺ cells (E) were identified in spleen. NIP⁺B220⁻ B cells (F), which represent plasma blasts and plasma cells, and NIP⁺CD138⁺B220⁻ B cells (G), which represent plasma cells, were identified in bone marrow cells. For B, C, and E (day 9), WT, n = 11; and SFR KO, n = 13. Data are pooled from four independent experiments (B and C). For D, WT, n = 4; and SFR KO, n = 5. Data are from one experiment. For E (day 18), WT, n = 4; and KO, n = 4. Data are from four experiments (day 9) or one experiment (day 18). For F and G, WT, n = 3 for day 16 and n = 4 for day 18; and SFR KO: n = 4 for days 16 and 18. Data are from one experiment. (H and I) Mice were immunized as in Fig. 2 B, except that NIP-reactive antibody-secreting cells were enumerated in spleen and bone marrow using an ELISpot assay. The protocol is detailed in H, and results are depicted in I. Representative pictures are shown on the left. Scale bar, 1 mm. Data from multiple independent mice are shown on the right (WT, n = 9; SFR KO, n = 9). Data are pooled from three independent experiments. Each symbol represents one mouse. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001 (two-tailed Student’s t test). Data are shown as mean ± SEM. ASC, antibody-secreting cell; BMC, bone marrow cell; D, day; FS, forward scatter.