In this regard, TRM lymphocytes have been reported to express molecules involved in cytotoxic activities, such as granzyme B, perforin, IL-2 and IFN-γ, as well as exhaustion markers such as PD-1 and CTLA-4 [40], likely representing tumor-specific effector cells induced by virus antigens [12, 41]. Here, PDCD1 is linked to neoplasm.