Batf^ΔZ/ΔZ B cells do not undergo CSR. (A) B cells purified from Batf^+/+ and Batf^ΔZ/ΔZ mice were cultured in media, or media supplemented with 20 µg/ml LPS, with or without 20 ng/ml IL-4. After 24 h, DNA synthesis was quantified by BrdU labeling for 16 h. Shown is mean BrdU incorporation, relative to Batf^+/+ or Batf^ΔZ/ΔZ cells in media (set to 1.0), from three experiments (n = 3) performed in triplicate. Error bars indicate SE. (B) B cells cultured as in A were assayed for surface Ig expression by flow cytometry (top) and for secreted Ig by ELISA (bottom). The mean and SE were calculated from three experiments (n = 3). N, not detected. (C) RNA from cells in B was assayed for the indicated transcripts using qPCR. Data are averaged from three experiments (n = 3) performed in triplicate and expressed relative to the Batf^+/+ media control (set to 1.0). Error bars indicate SE. N, not detected. (D) Sera from Batf^+/+ and Batf^ΔZ/ΔZ mice immunized with TNP-LPS or PBS were analyzed by ELISA for TNP-specific IgG1. Mean results from three mice per group (n = 3) are plotted. Error bars indicate SE. (E) Spleen sections from mice in D (n = 3 for each genotype) were stained as in Fig. 3 C to detect IgG1- and IgG2c-producing cells. Representative images are shown (20×). f, follicle. Bars, 50 µm.