CD4 and neoplasm: Figure 2C and 2D show that PD-1 expression and percentages of the CD4+ and CD8+PD-1hi T cells (Supplementary Figure S4A), were reduced in the spleens of tumor-bearing IDO-deficient mice, as well as the total percentages and ratio of total percentages to spleen weights of PD-1+ and PD-1hi CD8+ T cells.