Bone marrow B-lineage subpopulations collected on the basis of CD34, CD19, and IgM surface expression. (A) Cartoon illustrating each of the five subpopulations collected and the B-lineage developmental stage that each represents. Thick lines indicate higher levels of surface expression of the respective B-cell marker. (B) Typical collection gates used to separate the FBM subpopulations are shown in these FACS profiles of 22-week-old FBM stained with anti-CD34, anti-CD19, and anti-IgM as described in the Materials and Methods. (C) Typical collection gates used to separate the ABM subpopulations are shown in these FACS profiles of 30-year-old ABM stained with anti-CD34, anti-CD19, and anti-IgM as described in the Materials and Methods. (D) Typical postsort FACS analysis of the fetal CD34⁺ CD19⁻ subpopulation illustrating 99% purity in each subpopulation. Postsort analysis of the other fetal and adult subpopulations collected also indicated 99% purity (data not shown).