PDCD1LG2 and head and neck squamous cell carcinoma: Nazareth et al. also showed abundant levels of PD-L1 and PD-L2 in a subset of fibroblasts obtained from non-small cell lung carcinoma (32), and another study by Takahashi et al. showed a modest, but constitutive, expression of these ligands in fibroblasts from head and neck squamous cell carcinoma (11).