Although tumor immunotherapy benefits from high loads of tumor-specific mutations and high frequencies of neoantigen-specific CTLs7,9,55–57, natural neoantigen-specific CD8+ CTLs are often rare (e.g., 0.002–0.4% in melanoma, which already has the second highest tumor mutation loads58,59), likely due to low clonal neoantigen burden, inefficient antigen processing and cross presentation, and immunosuppression. Here, CD8A is linked to melanoma.