IL-7 expands native T-cells after T-cell–replete BMT. Bone marrow–derived newly developed T cells (CD45.1) and mature (supplemented) T cells (CD45.2) were distinguished by CD45-isoform and their absolute numbers were determined by flow cytometry at weekly intervals in peripheral blood samples. RAG-1^–/– mice (n = 30) received 5 × 10⁶ syngeneic T-cell–depleted CD45.1⁺ bone marrow cells, supplemented with 0.5 × 10⁶ CD45.2⁺ T cells. IL-7 was administered subcutaneously (500 ng twice daily) from day 7 to day 63. T-cell recovery was studied weekly, using single-platform flow cytometry, in PBS-treated mice (□,n = 15) and IL-7–treated mice (▪,n = 15). Mean absolute numbers (± SE) are shown for CD45.1⁺/CD3⁺ (A) and CD45.2⁺/CD3⁺(B) T cells.