MDSCs are critical for tolerance induction to allogeneic islets by donor ECDI-SPs. (A) Representative FACS plots depicting depletion of both populations of MDSCs (Gr1^HI-granulocytic MDSCs and Ly6C^HI-monocytic MDSCs) in the blood by the anti-Gr1 antibody. Upper panel: mice treated with isotype control antibody. Lower panel: mice treated with anti-Gr1 antibody. Dot plots were both gated on live CD11b⁺ cells. Dot plots shown were representative of a total of 4 mice in each group from 2 experiments. (B) Schematic treatment plan and percent graft survival with anti-Gr1 antibody treatment. ECDI-SP–treated transplant recipients further received either anti-Gr1 antibody or isotype control antibody (first dose: 200 µg/mouse; subsequent doses: 100 µg/mouse; IP) on the indicated days (N = 8, data were compiled from 3 independent experiments). *P < .05 (log-rank test).