PDCD1 and cancer: However, TILs often fail to eliminate cancer cells, as they progressively become dysfunctional or exhausted states, characterized by elevated expression of checkpoint molecules such as PD‐1, CTLA‐4, LAG‐3, TIM‐3, and TIGIT, among others.[11, 17, 70, 71, 72] This phenomenon mirrors the T cell exhaustion observed in mouse models of chronic antigen exposure, such as those induced by lymphocytic choriomeningitis virus (LCMV).[73, 74, 75]