Proliferation of BM-HSCs and DN1 thymocytes (thymus DN1) in OP9 stromal cell cocultures. (A) Isolation of stem cells from bone marrow and thymus by cell sorting. Bone marrow cells were pre-depleted for B220⁺, CD11b⁺, and Gr1⁺ cells, and thymocytes were pre-depleted for CD4⁺ and CD8⁺ cells by DYNAL magnetic bead separation. Stem cells were enriched to more than 96% purity by sorting for Lin^– cKit⁺/Sca1⁺ (BM-HSCs) or Lin^– CD44⁺/CD25^– (thymus DN1). (B) Proliferation of BM-HSCs or thymus DN1 after coculture on OP9-MigR1, OP9-Jagged1, or OP9-Delta1. Total cell recovery is plotted as fold increase over the initial number of stem cells seeded on day 0.