Loss of B cells in the absence of ASCIZ is not rescued by p53 deletion or complementation with the prearranged SWHEL BCR. (A and B) Absolute splenic B220⁺IgM⁺ B cell (A) and bone marrow B220^lowIgM⁺ immature B cell numbers (B) in Mb1/Mb1-Cre Asciz^fl/fl deleters (n = 10), Mb1/Mb1-Cre p53^fl/fl deleters (n = 8), Mb1/Mb1-Cre Asciz^fl/flp53^fl/fl double deleters (n = 15), and controls (n = 8). The control group contains four Mb1-Cre⁻Asciz^fl/flp53^fl/fl and four Mb1/Mb1-Cre Asciz^+/+p53^+/+ animals. The data were obtained in six independent experiments. (C and D) Absolute splenic B220⁺IgM⁺ B cell (C) and bone marrow B220^lowIgM⁺ immature B cell numbers (D) in Mb1/Mb1-Cre Asciz^fl/fl deleters (n = 7) and Mb1/Mb1-Cre Asciz^fl/fl deleters expressing a prearranged SWHEL IgH (HEL-IgH; n = 5), SWHEL IgL (HEL-IgL; n = 4), or both SWHEL IgH and IgL (n = 4), and Mb1/Mb1-Cre Asciz^+/+ controls expressing both SWHEL IgH and IgL (spleen n = 6; bone marrow n = 7). The data were obtained in three independent experiments. (A–D) Absolute numbers were determined by flow cytometry using gates as shown in Fig. 4. All grouped data represent mean ± SEM. Each symbol represents one animal.