Number of total cells and donor-derived cells in the recipient thymus after IV BM transfer.

T-cell– and mature B-cell–depleted C57BL/6 BM cells (25 × 10⁶) were injected intravenously into irradiated Ly-5.1 recipients. Thymocytes of the recipients were harvested at indicated days after BM transfer, stained with anti–donor type Ly-5.2 antibody, and analyzed by flow cytometry. Donor-derived cells were revealed by gating for Ly-5.2⁺ cells. An example of Ly-5.2 staining on the recipient thymocytes 4 days after primary BM transfer is shown by the solid line, and the isotype-matched background staining is shown by the dotted line in panel A. Number of total thymocytes per thymus (closed squares) was counted, and number of donor-derived cells (closed circles) was calculated from the proportion of Ly-5.2⁺ cells, as shown in panel B.