Reconstitution of peritoneal B1b cells in bone marrow chimeras. Bone marrow from adult WT, Itch^+/−, and Itch^−/− mice was transferred into sublethally irradiated Rag1^−/− recipients. (A) After 12 to 18 weeks, reconstitution of B2 (IgD^hiIgM^lo) and B1 (IgM^hiIgD^lo) cells was detected in the peritoneum. (B) The B1 population was comprised predominantly of B1b (Mac1⁺CD5⁻) cells with few B1a (Mac1⁺CD5⁺) cells. Data are representative of more than 5 experiments. The percentages of each population are indicated next to each gate.