Jagged2 mediates the T- versus B-cell lineage decision. (A) Jagged2, like Delta-like ligands, induces T-cell differentiation in human HPCs. Kinetic flow cytometric analysis of human CD34⁺CD38⁻lin⁻ CB precursors after coculture on OP9 stromal cells expressing the different human Notch ligands, as indicated above the dot plots. Numbers in quadrants indicate the frequency of the corresponding populations. Data shown are representative for 4 independent experiments. (B) Jagged2, Delta-like-1, and Delta-like-4 inhibit B-cell development. Dot plots show analysis of CD19 versus HLA-DR staining of human CD34⁺CD38⁻lin⁻ CB precursors cultured on OP9 stromal cells for 48 days. Dot plots shown are representative of 3 independent experiments.