Self-reactive Pik3cd GOF B cells spontaneously generate plasmablasts secreting high levels of autoantibody and form GC B cells. BM chimeras were generated as above. (A and B) Spleens were stained to identify SW_HEL IgM plasmablasts (IgM⁺CD138^hi). (C) Levels of anti-HEL IgM in the serum of chimeric mice. (D and E) Spleens were stained to identify SW_HEL GC B cells (Fas⁺CD38^lo). The center line shows the median, box limits show the upper and lower quartiles, and whiskers show the minimum and maximum (n = 15–23 mice per group, combined from nine experiments). Significant differences were determined using two-way ANOVA. ***, P < 0.001; ****, P < 0.0001. See also Fig. S5.