PDCD1 and neoplasm: To investigate whether PD‐1 signaling modulates the morphology of the mitochondrial network in tumor‐infiltrating T lymphocytes (TILs), we looked at PD‐1neg and PD‐1pos CD8+ T cells infiltrating an 18‐day‐old solid tumor mass derived from s.c. inoculation of MC38 cells (murine adenocarcinoma) in c57BL/6 WT mice.