CD4 and neoplasm: IDO‐positive patients had higher levels of tumor‐infiltrating Foxp3 + Treg cells (t = 8.686; P < .001, Figure 4A) and tumor‐infiltrating DC2s (t = 4.543, P < .001, Figure 4D), but a lower tumor‐infiltrating CD4/CD8 + T cell ratio (t = 2.323, P = .023, Figure 4B).