Fig. 1: Cfp1 loss impairs B cell activation and germinal center entry.

A, B Flow cytometry plots and ratio of splenic GCB (B220⁺CD95⁺GL7⁺) cells at different time post immunization with NP-KLH/Alum. Data were pooled from three independent experiments; Cfp1^fl/fl (Day5/10/14 n = 5; 3 males (m), 2 females (f)); Cfp1^fl/fl Cd21^Cre (Day5/10/14 n = 6; 3 m, 3 f). p < 0.0001 (10d = 7.68e–6, 14d = 4.50e–5). C The percentage of splenic GCB cells of Cfp1^fl/fl and Cfp1^fl/fl Cd21^Cre mice on day 14 p.i. with NP-KLH/MnJ. Data were from two independent experiments; Cfp1^fl/fl (n = 5; 3 m, 2 f); Cfp1^fl/fl Cd21^Cre (n = 6; 3 m, 3 f). D The percentage of splenic GCB cells of Cfp1^fl/fl and Cfp1^fl/fl Cd21^Cre mice on day 12 p.i. with SRBC. Data were from two independent experiments; n = 5; 3 m, 2 f. E, F ELISA for serum NP-specific low-affinity (NP₃₂) and high-affinity (NP₂) IgM and IgG1 antibodies from Cfp1^fl/fl and Cfp1^fl/fl Cd21^Cre mice on day 14 p.i. with NP-KLH/Alum; n = 5; 3 m, 2 f. G Representative flow plots and ratio of activated precursors (IgD^-B220⁺CD138^-GL7⁺CD38⁺) in the spleen of NP-KLH/Alum-immunized Cfp1^fl/fl and Cfp1^fl/fl Cd21^Cre mice analyzed on day 3. Data were pooled from two independent experiments; n = 5; 3 m, 2 f. p < 0.0001 (= 2.01e–5). H Representative flow plots and ratio of day 4 iGC B cells from Cfp1^fl/fl and Cfp1^fl/fl Cd21^Cre mice cultured on 40LB with the presence of IL-4. n = 5; 1 m, 4 f. p < 0.0001 (= 3.11e–10). I Cell cycle analysis of anti-CD40/IL-4/IL-21 stimulated splenic Cfp1^fl/fl and Cfp1^fl/fl Cd21^Cre B cells for 4d (red: G1; blue: S; green: G2/M). Data were pooled from two independent experiments; n = 5; 1 m, 4 f. p < 0.0001 (= 6.10e–8). J Representative histogram (red: Cfp1^fl/fl; blue: Cfp1^fl/fl Cd21^Cre) and quantification of CellTrace CFSE staining for cells in (I). Data were pooled from two independent experiments; n = 5; 1 m, 4 f. B, E, F Data points represent the mean ± SD. C, D, G, H, I, J Each symbol indicates one mouse and lines denote means. I Bars represent the mean. P-values by unpaired t-test (two-tailed).