IDO1 and neoplasm: To compare expression of IDO1 in tumor endothelial cells to that of tumor-infiltrating leukocytes, B16-F10 tumor bearing mice were treated with agonistic CD40 mAb or isotype control and CD45−CD31+ endothelial cells and CD45+ leukocytes were isolated using FACS before the start of therapy (day 12), one day after the last treatment (day 16) and four days after the last treatment (day 19).