DN1 and DN2 thymocytes do not develop to B cells on OP9 stoma in the presence of IL-7. Limiting dilution assay for sorted DN1 (▪) and DN2 (□) thymocytes and CD117⁺B220⁺ BM cells (○) was performed. Closed and open square symbols overlap demonstrating that both DN1 and DN2 thymocytes do not develop to B cells.