Engraftment in the absence of lymphocytes in the recipient, or in the absence of PD-L1:PD-1 signaling. (A) Scheme for analyzing engraftment of Lin⁻PD-L1⁺ and PD-L1⁻ FL cells in NSG mice. (B) Number of NSG recipients with engraftment, and with multilineage engraftment. 1 of 20 NSG recipients of 2E4 PD-L1⁺ FL cells and 5 of 6 recipients of 2E4 PD-L1⁻ FL cells had only lymphoid cell engraftment. Data were compiled from four separate experiments. (C) Donor contribution to total PB cells, B cells, T cells, monocytes, and granulocytes in NSG recipients. Solid horizontal lines indicate means ± standard deviation for PD-L1⁺ cells, and dotted lines for PD-L1⁻ cells. (D) Percentage ± standard deviation of donor-derived B (CD19⁺) and T (CD3e⁺) cells in all PB cells (donor + recipient) in NSG recipients. (E) Contribution of PD-L1⁺ and PD-L1⁻ FL cells, five mice per condition, to the PB of WT B6.SJL mice. Mean ± standard deviation is shown. (F) Contribution of PD-L1⁺ and PD-L1⁻ FL cells to HSPCs in the BM of NSG recipients. Mean ± standard deviation is shown. (G) Schematic for comparing engraftment of embryonic HSCs in WT and PD-1–null recipient mice. (H) Donor contribution of cells from the AUV of E11.5 WT (B6.SJL) embryos to HSPCs in the BM of WT (C57BL6/J) and PD-1–null recipient mice. Data were compiled from transplanting into 9 C57BL6/J and 10 PD-1–null recipients in two separate experiments. Mean ± standard deviation is shown.