Sustained T cell development and T cell export visualized by RAG2p-GFP reporter. (A) Newborn thymi from RAG2p-GFP reporter mice were transplanted into Rag2^−/−γ_c^−/−Kit^W/Wv recipients. RAG2p-GFP control thymus, 2 RAG2p-GFP grafts 10 wk after transplantation (graft A and graft B are two lobes from the same thymus that were separated at the time of transplantation), and the endogenous thymus of the Rag2^−/−γ_c^−/−Kit^W/Wv host are shown. Expression of CD4 and CD8 was analyzed in CD45.1⁺ donor cells, gated for GFP⁺ and GFP⁻. Plots are representative of one out of four experiments, each with four to seven recipients. (B) CD45.1⁺CD3⁺ cells from peripheral blood of a B6/Ly5.1 control and from a representative Rag2^−/−γ_c^−/−Kit^W/Wv host bearing RAG2p-GFP grafts are shown. A total of 19 recipient mice were analyzed at the indicated time points in weeks (w) for the presence of GFP⁺CD4⁺ (top row) and GFP⁺CD8⁺ (bottom row) recent thymic emigrants. Numbers indicate percentages of cells in each quadrant.