PDCD1 and neoplasm: Therefore, we employed high dimensional flow cytometry to assess the diversity of the CD8+ T cell compartment, looking at markers of memory and effector differentiation (CD45RA, CCR7, CD27, CD28, CD127, CX3CR1, and CD161), activation (OX40, CD25, CD69, and HLA-DR), inhibitory receptors (PD-1 and TIGIT), tissue residency and tumor reactivity (CD103 and CD39) and effector molecules (GZMB and GZMK).