IDO1 and head and neck squamous cell carcinoma: This supervised approach highlighted that HNSCC-cDC2 overexpressed several Secretory cDC-specific markers identified previously at the protein level, such as CD274/PD-L1, PDCD1LG2/PD-L2, PVR, CD40 (Fig. 2D, E), IL1B, IL12B, IL23A, TNF, and CCL19 (Fig. 3B, Supplementary Fig. 6), and other negative checkpoints such as IDO1, IDO2, and HAVCR2/TIM3, the migration marker CCR7, the maturation marker LAMP3, and NFKB1 (Fig. 4F).