Infant B cells are intrinsically unable to form TI GCs. (A) The protocol. B1-8hi GFP+ cells from adult (8–12 wk) or infant (3 wk) mice were transferred into either adult or infant recipients as indicated, and TI GCs were constructed by i.p. NP30-Ficoll immunization. (B–G) FACS dot plots and summary statistics show TI GCs (B and C), PCs (D and E), and Bmem cells (F and G) in the spleen of recipients, 5 d after immunization. Data were pooled from two independent experiments with at least three mice per group. Each symbol indicates one mouse, and lines denote means. P values by t tests. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.