Bim-deficient mice accumulated abnormally increased numbers of memory B cells. Wild-type and bim^−/− mice were immunized with NP. Spleen cells were harvested after 7, 14, and 28 days and analyzed for their content of IgM⁻IgD⁻Gr-1⁻Mac-1⁻B220⁺IgG1⁺NP⁺ B cells by flow cytometry (as in Figure 1A). Within this cell population, cells with a memory phenotype (CD38^high) and GC phenotype (CD38^low) were quantified by FACS analysis (as in Figure 1A). The total numbers of memory B cells in the spleen (A; *P < .05), percentages of memory B cells in the blood (B), total numbers of GC B cells in the spleen (C; *P ≤ .05) and the percentages of GC B cells in the blood (D) are indicated. Data represent the mean (± SD) of n = 4 to 8 mice.