Tumor-infiltrating neoantigen-reactive T cells commonly exhibit high expression of exhaustion markers such as programmed cell death protein 1 (PD-1), T-cell immunoglobulin and mucin-domain containing-3 (TIM-3), T-cell immunoglobulin and ITIM domains (TIGIT), and Lymphocyte-activation gene 3 (LAG-3), due to the chronic and persistent antigen stimulation they experience within the immunosuppressive tumor microenvironment (TME). Here, PDCD1 is linked to neoplasm.