Overactive PI3K breaks peripheral B cell tolerance, enabling expansion and persistence of self-reactive B cells. BM chimeras were generated as above; spleens were harvested and analyzed by flow cytometry 8–15 wk later. (A) Representative plots of SW_HEL B cells and of transitional (CD93⁺) and mature (CD93⁻) B cells. Numbers give each subset as a percentage of total B cells (mean ± SEM of all mice). (B) Graphs show percentages of total SW_HEL and mature SW_HEL cells among splenic lymphocytes. (C) Representative plots gated on mature SW_HEL cells, showing the percentages (mean ± SEM of all mice) of follicular (CD23⁺CD21^med) or MZ (CD23⁻CD21^high) among total B cells. (D) Graphs show percentage of follicular and MZ SW_HEL cells among all splenic lymphocytes. In B and D, the center line shows the median, box limits show the upper and lower quartiles, and whiskers show the minimum and maximum. All panels represent n = 11–20 mice per group combined from five to nine experiments. Significant differences were determined using two-way ANOVA. *, P < 0.05; ***, P < 0.001; ****, P < 0.0001. See also Fig. S3.