Lack of expansion of B1 cells in B6.Aia3 congenic mice. Peritoneal cavity cells from 2- and 8-month-old B6 and B6.Aia3 Yaa male mice and 2-month-old NZB female mice were stained with a combination of anti-B220, anti-CD5, and anti-CD11b mAb. Representative staining profiles for the CD5 and CD11b on B220⁺ B cells from the indicated mice (3 to 5 mice in each group) are shown. Mean percentages (±SD) of B1a (CD5⁺CD11b⁺) and B1b (CD5^–CD11b⁺) subsets are indicated.