reported that the PD-1+CD8+ TIL population recognized and killed autologous tumor cells compared with their negative controls in six tissues from patients with metastatic melanoma (MM), and the PD-1+CD8+ TIL population with specific TCRβ clonotypes contained clonotypes targeting mutant antigens and reserved the ability to recognize autologous tumor cells, showed highly monoclonal expansion. Here, PDCD1 is linked to metastatic melanoma.