200 μg of anti-Gr1 mAb (anti-mLy-6G, clone RB6-8C5) was given i.p. on day −8, and additionally 100 μg on days −7, −3, −1, and +1. ECDI-SPs were given on day −7 and day +1. Cardiac transplant was performed on day 0. A: Heart grafts were retrieved on day 7, sectioned and stained for IDO as in FIG. 2A. IDO+ cells were enumerated from 8 sections under low power view by 2 different individuals. Results were averaged and presented as the bar graph shown. B: Effect of anti-Gr1 mAb on cardiac graft protection by ECDI-SPs treatment. Graft survival in groups treated with anti-Gr1 mAb alone or ECDI-SPs alone was shown for comparison. C: FACS analysis of cells from cardiac grafts (top panels) or the spleen (lower panels) from control vs. ECDI-SPs treated recipients (day 7 post transplantation). Plots were gated on live cells. Data presented is representative of 4 mice examined from each group in two different experiments. D: Dual staining of day 7 cardiac grafts with Gr1 (dark blue) and IDO (brown). Top panel: control graft; middle and lower panels: ECDI-SPs graft. Magnifications are shown on the micrographs.