Five million WT miECs and five million B2m^?/?Ciita^?/? miECs or B2m^?/?Ciita^?/? Cd47 tg miECs were mixed and stained with 5 µM CFSE (Thermo Fisher). Cells in saline were injected i.p. into syngeneic C57BL/6 mice, CD11b-DTR mice or Sirpa^?/? mice. Some mice received a coinjection i.p. with 1 µg mouse IL-2 or mouse IL-15 (PeproTech). After 48 h, cells were collected from the abdomen and stained with PerCP-eFlour710–labeled anti-MHC class I (clone AF6-88.5.5.3, mouse IgG2a,κ; eBioscience) mAb for 45 min at 4°C. The CFSE-positive and MHC class I–negative population was analyzed by flow cytometry (FACSCalibur; BD Biosciences) and compared between the WT and the engineered miEC group. All animals were pretreated 18 h with poly I:C injection (100 µg in sterile PBS i.p.; Sigma-Aldrich) before miEC injection. Some animals were pretreated with clodronate (200 µl i.p. 3 d before the experiment; Liposoma) to eliminate macrophages and make the assay more specific for NK cells. Some animals were pretreated with anti-NK1.1 (clone PK136, 200 µl i.p. 3 d before the experiment; BD Biosciences) to eliminate NK cells for macrophage-specific experiments. Some animals received clodronate and anti-NK1.1 for cell depletion. Some of the CD11b-DTR mice were pretreated with DT (Lystlab) 3 d and 1 d before the experiment at a concentration of 25 ng/g mouse weight in 100 µl saline i.p. For peritoneal transfer, 10⁶ peritoneal cells from naive C57BL/6 mice were injected on day 0 with the target miECs. Some animals were pretreated with an anti-Cd47 blocking antibody (clone MIAP301, rat IgG2a,κ; BioXCell; 100 µg i.p., 2 d before implantation of the miEC). Some animals were pretreated with an anti-Sirpα blocking antibody (clone P84, rat IgG1,κ; BioLegend; 100 µg i.p. 2 d before implantation of the miEC). To investigate mouse in vivo innate killing of B2m^?/?Ciita^?/? miECs and B2m^?/?Ciita^?/? Cd47 tg miECs, 5 × 10⁶ of both cells were injected after staining with DiO and DiD, respectively according to the manufacturer’s protocol (Vybrant Multicolor cell labeling kit; Invitrogen). Syngeneic C57BL/6 mice were pretreated 18 h with poly I:C (100 µg i.p.; Sigma-Aldrich) in saline before cell injection. After 48 h, cells were collected from the peritoneum and analyzed by flow cytometry (FACSCalibur; BD Bioscience).