PDCD1LG2 and head and neck squamous cell carcinoma: Ligand-specific IcAR scores revealed possible explanations for different treatment lines: patients expressing high functional PD-L2, crucial for HNSCC outcomes18,19, were mainly among first-line recipients, while of those in the PD-L1 positive PD-L2 negative group, a notable 71%, were in the second- and third-line groups.