Cell-intrinsic requirement for ASCIZ during B cell development. (A) FACS analysis of spleen cells of lethally irradiated Ly5.1 recipients 8 wk after transplantation with Ly5.2 control or Mb1/Mb1-Cre Asciz^fl/fl deleter bone marrow and percentage of B220⁺IgM⁺ B cells among donor-derived spleen cells (control transplants, n = 8; deleter transplants, n = 8). Half of the control transplants were performed with bone marrow from a single Mb1/Mb1-Cre Asciz^+/+ donor, the other half with bone marrow from a single Mb1-Cre⁻Asciz^fl/fl donor. Two different deleter bone marrows were used for four different recipients each. (B and C) Percentages of donor-derived pre-B and immature B cells in bone marrows from the same recipients shown in A. (A–C) Error bars represent mean ± SEM. Each symbol represents one animal. All data were obtained in one experiment.