CD5⁺B-cell expansions in the spleens of Eμ^CycD1CD19^CREBim^fl/flmice subjected to SRBC injection. Mice of the indicated genotypes were injected with SRBC and evaluated by gross examination and flow cytometry. (A) Eμ^CycD1CD19^CREBim^fl/fl mice developed larger spleens than WT and Eμ^CycD1 mice, but all other groups were statistically similar. (B) Eμ^CycD1 and Eμ^CycD1CD19^CREBim^fl/fl mice manifested larger mediastinal lymphadenopathy (LAD) compared with WT mice; no other statistically significant differences were observed among the other groups. (C) Flow cytometry determined the percentage of splenic mononuclear cells that were positive for CD5 and either CD19 or B220. WT (n = 5), Eμ^CycD1 (n = 5), CD19^CREBim^fl/fl (n = 4), and Eμ^CycD1CD19^CREBim^fl/fl (n = 5). Data are mean and standard error of the mean. *P < .05; **P < .01; ***P < .001; 2-tailed Student t test.