LNs contain lymphoid progenitors committed to the T lineage. RT-PCR analysis of DN1 (A), pre-DN2 (B), and DN4 (E) cells sorted from wt thymus, wt LNs, and OM⁺ LNs. One-step RT-PCR was done on the same mRNA samples for transcripts of interest and for Hprt. (C) c-Kit expression on DN2 and DN3 subsets from wt thymus (dotted line) and OM⁺ LNs (solid line). Intracellular TCRβ (icTCRβ) chain expression in DN3 (D) and DN4 (F) subsets. (G) Sorted DN4 cells (10⁵; Lin^–CD8^–CD44^–CD25^–) harvested from wt LNs were cocultured on OP9-DL1 cells and analyzed for T-cell development after 7 days of in vitro culture. Numbers indicate cell population percentages. In panels F and G, dotted lines represent staining with isotype control antibodies.