PDCD1 and neoplasm: On the other hand, among CD4+ and CD8+ T cells in the tumor microenvironment (TILs), those with low/undetectable CD5 exhibited higher levels of measures of activation compared to CD5high TILs although CD8+ TILs displayed a more uniformly high display of markers of activation/effector activity (elevated PD-1, CD69, CTLA-4, IFNγ, CD107a, and CD137) associated with low CD5 than did CD4+ TILs (elevated CD69, CD107a, and CD137 but lower PD-1 and no significant change in CTLA-4): an observation suggesting a more complex relationship between activation and CD5 in CD4+ TILs.