Fig 1: Co-culture assays of HEK-hIDO1 cells with lymphocytes from a healthy donor. Proliferation of CFSE-labeled CD8-positive T cells co-cultured for 5 days with HEK-hIDO1 cells upon addition of (A) 200 µM Trp as a positive control for T cell proliferation, (B) 10 µM NTRC 3883-0, and (C) 1 µM epacadostat. Each panel shows an overlay with CD8-positive T cells co-cultured for 5 days with HEK-hIDO1 cells upon addition of 7.5 µM Trp and vehicle (left), and the cell proliferation analysis (right). PF, precursor frequency (the percentage of cells from the original population that have proliferated); PI, proliferation index (the average number of cell divisions undergone by the proliferating cell population); DI, division index (the average number of cell divisions undergone by the entire cell population). The percentages indicate the percentage of the total amount of cells in each generation.