Immunophenotype of cells differentiated in vitro from CD34⁺CD10^–CD19^– human cord blood progenitors. (A) Kinetics of expression of the B-cell markers CD79a and CD19 on CD34⁺CD10^–CD19^– progenitors (day 0) incubated in stromal-based cultures with SCF, IL-2, and IL-15. Nonadherent and adherent cells were collected at days 7, 14, and 21; cells were first incubated with PE-Cy5–coupled anti-CD19 MoAb and then permeabilized and labeled with APC-coupled anti-CD79a MoAb. Limits for positivity and negativity were defined by incubating cells with nonimmune isotypic-matched immunoglobulin. (B) Staining profiles of CD79a⁺CD19^– and CD79a⁺CD19⁺ cells at day 14. Nucleated cells collected from the cultures were subjected to 3-color labeling. Anti-CD79a and anti-CD19 were systematically included and associated to a third antibody recognizing HLADR, CD7, CD34, CD10, CDw127, and CD38 (not shown). Both CD79a⁺CD19^– cells and the companion CD79a⁺CD19⁺ fraction were simultaneously analyzed for the expression of these markers using a FACScalibur and CellQuest software. Results are shown from 1 of 4 similar experiments with similar results. Mean (SD) percentages of at least 4 experiments are indicated.