Otherwise, tumor-infiltrating lymphocytes (TILs) produce high levels of programmed cell death protein 1 (PD-1) and interact with its specific ligand, known as programmed cell death ligand 1 (PDL-1) overexpressed by PDAC cells, resulting in T lymphocyte depletion (Figure 3) [68, 69]. This evidence concerns the gene PDCD1 and neoplasm.