TCR150-transgenic PBL recognition of HLA-A2⁺ HSCs. (A) In vivo reconstitution of pre-irradiated HHD mice with Sca-1⁺–enriched HHD HSCs. Isolated stem cells were cocultured with GFP- or TCR150-transgenic lymphocytes at an effector-to-target ratio of 1:1 before transfer (1 × 10⁶ stem cells intravenously). As controls, mice were injected with GFP-transduced splenocytes alone or no cells. Mice were monitored for signs of radiation syndrome and were removed from the study when weight loss was greater than 30%. (B) CFU assay using CD34⁺-enriched human HSCs from either HLA-A2⁺ or HLA-A2⁻ healthy donors as target cells. 1.25 × 10⁴ HSCs were cocultured with 1 × 10⁵ TCR150-transgenic or mock-treated PBLs. After 2 weeks, duplicate cultures were analyzed for the development of differentiated cell colonies. CFU-E indicates CFUs erythroid; BFU-E, burst-forming-units erythroid; CFU-G, CFUs granulocyte; CFU-M, CFUs macrophage; CFU-GM, CFUs granulocyte and macrophage; and CFU-GEMM, CFUs granulocyte, erythroid, macrophage, and megakaryocyte.