In particular, antibody drugs that block negative regulators of the immune system such as cytotoxic T lymphocyte antigen 4 (CTLA-4), programmed cell death 1 (PD-1), and programmed cell death 1 ligand 1 (PD-L1) have been shown to be effective in malignant melanoma and squamous cell carcinoma of the lung, and their efficacy has been verified in a variety of carcinomas [4–7]. Here, PDCD1 is linked to melanoma.