B-cell changes begin early in bone marrow development. (A) Flow cytometry staining of bone marrow B cells is based on the Hardy classification system and was conducted as described in the “Methods” section, cells are gated on live lymphocytes for analysis. Representative dot plots and summary data are shown for LMC and mb1^DPWY bone marrow. (B) Summary data for the percentage of B220⁺ cells in total bone marrow. (C) The percentage of CD43⁻ vs CD43⁺ B220 expressing cells in the total bone marrow of mb1^DPWY vs LMC showing proportionally fewer more mature (CD43⁻) B cells present in the bone marrow of mb1^DPWY mice. (D) The percentage of each developmental subset (A-F) in the total bone marrow of mb1^DPWY vs LMC showing the significant loss of B cells in fraction C onward. Cells are gated on live lymphocytes for analysis. Summary data of bone marrow subsets are for n = 9 mb1^DPWY and n = 9 LMC from 3 independent experiments; data are shown as the mean ± SEM. *P < .05, **P < .01, ***P < .001.