OP9 cocultures. (A) Development of CD4⁺CD8⁺ double-positive cells from CD34⁺CD1a^– (left) and CD34⁺CD1a⁺ (right) thymocytes cultured for 14 days on OP9-DL1; 1000 cells per well were seeded. (B) Cell numbers per well after 14 days of culturing 1000 CD34⁺CD1a^– or CD34⁺CD1a⁺ thymocytes on OP9-GFP or OP9-DL1. (C) CD7 staining of 300 CD34⁺CD1a^– thymocytes cultured on OP9-GFP (left) or OP9-DL1 (right) for 14 days. (D) Presence of CD19⁺ B cells and/or CD13/33⁺ myeloid cells in 14-day cocultures of 300 CD34⁺CD1a^– thymocytes on OP9-GFP (left and middle) or on OP9-DL1 (right).