ICOSLG and head and neck squamous cell carcinoma: Of note, when we assessed which APC population expressed transcripts for these ligands, some were found in multiple subsets in both OM and HNSCC (for example, TGFΒ1, IL1B and CXCL16), whereas ICOSLG was found only on cDC1s from the HNSCC (Fig. 2g, Extended Data Fig. 6b).