Cytotoxicity against host cells and GVL activity of donor T cells are enhanced when CD73 is deficient or inhibited. (A) A total of 5 million BM cells with (BMS) or without (BM) 15 × 10⁶ splenocytes from Cd73^+/+ or Cd73^−/− BALB/c mice were transplanted into irradiated Cd73^+/+ or Cd73^−/− C57BL/6 recipients, respectively. Six to 7 days later, equal numbers of CFSE-labeled B cells from Cd73^−/− C57BL/6 and Cd73^−/− BALB/c mice were transferred intravenously into the recipients as targets. Three hours later, recipient spleens were harvested and the CFSE-labeled cells were analyzed for the expression of H-2K^b and H-2K^d by flow cytometry. A decrease in the percentage of CFSE⁺ H-2K^b target cells is indicative of anti-host cytotoxic activity. The data are summarized as the percentage (mean ± SD) of total CFSE-labeled target B cells that are H-2K^b+ (n = 3 or 4). *P < .05. (B) Lethally irradiated BALB/c mice received 5 × 10⁶ C57BL/6 BM cells and 5 × 10⁴luc⁺ A20 cells on day 0 of allo-HCT and 3 × 10⁵ C57BL/6 CD4⁺/CD8⁺ splenic T cells on day 2. One group (n = 6) was treated with the CD73-inhibitor APCP at a dosage of 50 mg/kg per day intraperitoneally. On days 0 to 10 after allo-HCT, the other group (n = 6) received an equal volume of PBS as vehicle. Expansion of luc⁺ A20 cells was monitored via BLI as described in “In vivo BLI.” Representative bioluminescent images on days 6, 9, and 12 are shown. (C) Expansion of luc⁺ A20 tumor cells as measured in photons over total body area at different time points with 6 mice per group is shown. Data from one of 2 independent experiments with similar results are shown (mean ± SEM). (D) Same as in panel B, except that the recipient mice received WT A20 tumor cells and only 10⁵ CD4⁺/CD8⁺ splenic T cells. A control group of mice did not receive A20 tumor cells. Survival was monitored for 5 weeks. Data are pooled from 2 independent experiments (n = 10 or 11/group). P = .0005 (PBS vs APCP treatment).