Figure 4.

Adoptive transfer of mouse proT cells into lethally-irradiated aged mice. A schematic for experiments is shown (A). LSK/OP9-DL co-cultures were initiated 10 days prior to injection. 18-month old (Aged) and 3-month old (Young) wild-type C57BL/6 (CD45.2) mice were irradiated at 1.025 Gy on the day of injection. All irradiated mice were intravenously injected with 1 × 10⁶ cells extracted from GFP⁺ BM. In addition to the bone marrow cells, some mice also received 6 × 10⁶ proT cells harvested from 10 day co-culture of OP9-DL/BM LSK cells from congenic mice (CD45.1⁺) (n = 3 or 4 per group). Plots show the analysis of thymuses that were dissected on 7 (B) and 14 days (C) after injection. Thymocytes were stained with the appropriate cell lineage markers and analyzed by flow cytometry. Plots showing host-derived cells (CD45.2) are shaded in blue, proT cell-derived cells (CD45.1) are shaded in orange and BM graft-derived GFP⁺ cells are shaded in green. Bone marrow analysis of the corresponding mice in C show contribution of GFP⁺ BM grafts to the BM of the irradiated host on D14 (D). Total thymocyte number was analyzed on D14 (E). The error bars correspond to SEM (*p < 0.05, two-tailed unpaired student's t-test).