Donor derived DN1 CD122⁻NK1.1⁻ thymocytes differentiate into NK cells in the thymus. (A) Thymic DN1 CD122⁻NK1.1⁻ cells from Rag1^−/− mice were sorted and collected for post sort analysis with the gating parameters shown. (B) Thymi from Rag1^−/− Ly5.2 mice were harvested and sorted based on DN1CD122⁻NK1.1⁻ phenotype as shown in panel A. Cells were transferred into irradiated Rag1^−/− Ly5.1 mice either intravenously or intrathymically. Irradiated littermates were used as controls. Cells were harvested from the thymus 32 days after transfer. NK1.1⁺ cells from the lymphocyte population were then examined for host (Ly5.1⁺) and donor (Ly5.2⁺) cells. Data are representative of 2 experiments.