(A) Splenic CTV-labeled MZ and follicular (FO) B cells were sort purified from B6.Blimp1^GFP/+ mice and stimulated in culture with CpG + IL-4 and IL-5 with and without the indicated cell cycle inhibitors. Resulting cells were analyzed by flow cytometry after 48 or 72 hours as indicated. Summary data are individual values, mean ± SEM. ***Adjusted P < 0.001, 2-way ANOVA, Sidak test for multiple comparisons between cell types. (B) FO B cells stimulated as in A with titrated concentrations of aphidicolin were evaluated at 72 hours. Histogram overlay shows CTV dilution at each aphidicolin concentration and graph shows percentage of GFP⁺ cells as a function of all viable cells at each division number. Line shows mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, compared with vehicle control using 2-way ANOVA Tukey test. (C) Cells prepared as in A were stimulated for 72 hours in culture with CpG plus IL-4 and IL-5 with or without PD0332991 or rapamycin. Graded numbers of cells from control cultures that had divided thrice, or undivided cells from cultures containing inhibitors were sorted and added to ELISpot plates. Summary data are individual values, mean ± SEM. **FDR q < 0.01, multiple t tests, 2-stage linear step-up procedure of Benjamini, Krieger and Yekutieli, with Q = 5%.