Elderly female mice contain an enlarged population of CD19⁺CD11b⁺CD11c⁺ B cells (ABCs). (A) Flow cytometric analysis of total spleen (left set of plots) or splenic B cells (gated as IgM⁺B220⁺CD4⁻CD8⁻NK1.1⁻; right set of plots) in young (< 12 weeks old) and elderly (> 1 year old) C57BL/6 mice. Data are representative of > 10 independent analyses. (B-C) Average percent and number of CD19⁺CD11b⁺CD11c⁺ cells in spleen of male (blue) and female (pink) C57BL/6 mice. *P < .01 (Student 2-tailed t test). (D) Flow cytometry of FO B cells (CD19⁺CD11b⁻; black) and CD19⁺CD11b⁺ B cells (red).